core.dtypes.generic --> cython
Implement `ABCFoo` classes in cython.

Small optimization of the `typ in comps` check.  When `comps` is a singleton, this just becomes `typ == comp`.  I considered and decided against trying to take advantage of string interning to make it `typ is comp`.

Naturally asv is refusing to run (current hypothesis is it has something to do with a new directory existing), but in %timeit tests its an across-the-board speedup ~50%.

A new asv file is included in case someone else wants to try running it.

Hello @jbrockmendel! Thanks for updating the PR.









Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on September 29, 2017 at 16:59 Hours UTC i seen u added the asv

pls run it / you need to figure how to run these stably # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=h1) Report
> Merging [#17599](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/21a38008e3cab7a0459cce4fab4ace11379c3148?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17599/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17599      +/-   ##
==========================================
- Coverage   91.19%   91.17%   -0.03%     
==========================================
  Files         163      163              
  Lines       49626    49601      -25     
==========================================
- Hits        45258    45224      -34     
- Misses       4368     4377       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.96% <100%> (-0.01%)` | :arrow_down: |
| #single | `40.16% <100%> (-0.1%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2dlbmVyaWMucHk=) | `100% <100%> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=footer). Last update [21a3800...2addb85](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=h1) Report
> Merging [#17599](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e2a0251d32a1467e9ab86281a31f57aca582a88f?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17599/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17599      +/-   ##
==========================================
- Coverage   91.27%   91.24%   -0.03%     
==========================================
  Files         163      163              
  Lines       49765    49740      -25     
==========================================
- Hits        45421    45387      -34     
- Misses       4344     4353       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.04% <100%> (-0.01%)` | :arrow_down: |
| #single | `40.3% <100%> (-0.1%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2dlbmVyaWMucHk=) | `100% <100%> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.73% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=footer). Last update [e2a0251...e46760c](https://codecov.io/gh/pandas-dev/pandas/pull/17599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 > you need to add in the list of installed dirs

Yep, that fixed the asv problem.

```
asv continuous -f 1.1 -E virtualenv master HEAD -b generic_dtypes
[...]
       before           after         ratio
     [21a38008]       [2addb85f]
-       201±0.8μs          143±1μs     0.71  generic_dtypes.GenericDtypes.time_isinstance

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
``` can u show the result of the asv. Closing this to de-clutter the queue, may circle back to it when things calm down.