Add Basic Travis CI Format Checks

[bashbaug]

Observed Behavior

It's easy for new contributors to inadvertently introduce formatting inconsistencies into this codebase.

Desired Behavior

Add automated checks for basic formatting inconsistencies, such as use of tabs vs. spaces, or trailing whitespace.

Steps to Reproduce

Create a pull request with tabs or tailing whitespace. Travis CI and Appveyor both run but only verify that the build succeeds, and no formatting checks are performed.