BUG: Validate the skipfooter parameter in read_csv
Previously, the `skipfooter` parameter was assumed to be an integer, but that was not checked.

xref <a href="https://github.com/pandas-dev/pandas/pull/15925#discussion_r110283317">#15925 (comment)</a>

@jreback : Seemingly unrelated OSX failure has emerged on `master` after your commit <a href="https://github.com/pandas-dev/pandas/commit/d60f490b4e764ab9af170adf4d88639014804fe6">here</a>. yeah been happening in several builds
restarting has mostly fixed  @jreback : Hmm...okay, let me know once `master` starts passing again.  Then I'll resubmit for building.  Otherwise, it is ready to merge. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=h1) Report
> Merging [#15945](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d60f490b4e764ab9af170adf4d88639014804fe6?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/15945/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #15945      +/-   ##
==========================================
+ Coverage   90.99%   90.99%   +<.01%     
==========================================
  Files         145      145              
  Lines       49565    49569       +4     
==========================================
+ Hits        45101    45105       +4     
  Misses       4464     4464
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.76% <100%> (ø)` | :arrow_up: |
| #single | `40.56% <14.28%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.65% <100%> (+0.01%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15945?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/15945?src=pr&el=footer). Last update [d60f490...baa3415](https://codecov.io/gh/pandas-dev/pandas/pull/15945?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments). @jreback : Oh, seems like the rebuild finished successfully.  All green and ready to go now. i restarted build thanks!