DOC:Improved the docstring of pandas.melt
Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [ ] PR title is "DOC: update the <your-function-or-method> docstring"
- [ ] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
- [ ] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] The html version looks good: `python doc/make.py --single <your-function-or-method>`
- [ ] It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

```
# paste output of "scripts/validate_docstrings.py <your-function-or-method>" here
# between the "```" (remove this comment, but keep the "```")

```

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.


Checklist for other PRs (remove this part if you are doing a PR for the pandas documentation sprint):

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @elitsaLe! Thanks for submitting the PR.

 - In the file [`pandas/core/reshape/melt.py`](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py), following are the PEP8 issues :

> [Line 27:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L27): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 28:69](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L28): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 29:72](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L29): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 30:73](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L30): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 31:74](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L31): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 33:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L33): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 41:74](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L41): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 42:36](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L42): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 49:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L49): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 53:48](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L53): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 54:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L54): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 59:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L59): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 71:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L71): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 77:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L77): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 86:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L86): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 88:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L88): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 95:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L95): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 97:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L97): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 105:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L105): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 111:1](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L111): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 116:42](https://github.com/pandas-dev/pandas/blob/0a21c16308281ec434d32dc87cfe0eaa5cfe10c9/pandas/core/reshape/melt.py#L116): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace

 WIP:melt.py
This file does not pass validation. The errors that the validation reports do not exist in the modified file. @elitsaLe let us know if you want to continue working on this.