Adding StyleGuide enforcement for Hound

Per a developer conversation, we are going to expand our character
line length guide from 80 characters to 140 characters.

Fundamentally, we are asking that Rubocop run against the files you
are changing:

    $ rubocop ./path/to/file_1 ./another/path -c ./.hound.yml

Hound enforces that on your pull request.
Adding documentation on how to run rubocop

[skip ci]
Merge pull request #520 from projecthydra-labs/adding-hound-style-guide-enforcement

Adding StyleGuide enforcement for Hound