Clarify whitespace behavior in read_fwf documentation (#16772)
 - [x] closes #16772 
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master -u -- "*.py" | flake8 --diff``
 - [ ] whatsnew entry

Hello @lphk92! Thanks for updating the PR.





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

##### Comment last updated on July 17, 2017 at 23:31 Hours UTC cc @chris-b1 

hmm so we are updating the docs? was there a resolution on the issue? # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@4c498f8`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16950/graphs/tree.svg?height=150&width=650&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #16950   +/-   ##
=========================================
  Coverage          ?   90.96%           
=========================================
  Files             ?      161           
  Lines             ?    49288           
  Branches          ?        0           
=========================================
  Hits              ?    44837           
  Misses            ?     4451           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.74% <ø> (?)` | |
| #single | `40.2% <ø> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.43% <ø> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16950?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/16950?src=pr&el=footer). Last update [4c498f8...46f7af9](https://codecov.io/gh/pandas-dev/pandas/pull/16950?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/16950?src=pr&el=h1) Report
> Merging [#16950](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/81f8acef11e8d1e2f0ea78a7b57ee04bef1f6038?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16950/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16950      +/-   ##
==========================================
+ Coverage   90.99%      91%   +<.01%     
==========================================
  Files         161      161              
  Lines       49289    49289              
==========================================
+ Hits        44850    44853       +3     
+ Misses       4439     4436       -3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.77% <ø> (+0.02%)` | :arrow_up: |
| #single | `40.18% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.43% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.76% <0%> (-0.1%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.05% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16950?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/16950?src=pr&el=footer). Last update [81f8ace...3cce472](https://codecov.io/gh/pandas-dev/pandas/pull/16950?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback : AFAICT, I think @chris-b1 was thinking we should better surface and document the `delimiter` parameter, which I agree with and is what this PR does. This looks good to me, except for doc notes.  I didn't know the delimiter kw worked this way on `read_fwf`, so not what I had in mind, but is the right solution! lgtm. merge on green. @lphk92 : If you could address my question <a href="https://github.com/pandas-dev/pandas/pull/16950#discussion_r127601576">above</a> before merging this, that would be great! @gfyoung I've just responded to your question as best I can. Let me know if I can provide more clarification. Alright, everything looks good now.  Merging. Thanks @lphk92 !