PEP multiline docstrings

[lwasser]

Following @mbjoseph comment in this pr

Super minor thing but do we want to adhere to PEP 257 for multiline docstrings? https://www.python.org/dev/peps/pep-0257/#multi-line-docstrings

I'm thinking specifically about this bit: 

    Multi-line docstrings consist of a summary line just like a one-line docstring, followed by a blank line, followed by a more elaborate description. 

let's talk about whether we want to implement this throughout earthpy - this would include the functions AND the tests!!

[mbjoseph]

Here's an example: https://github.com/earthlab/earthpy/blob/master/earthpy/spatial.py#L350-L395

[lwasser]

We will implement following the example above for bytescale pep 257 format with a short overview and a longer description as it's needed.

[PowerChell]

I believe this issue was addressed in PR #246