Setup cpplint CI test

[ariddell]

cpplint: https://github.com/google/styleguide/tree/gh-pages/cpplint

I think this isn't difficult to do. Perhaps Stan has done this already?

[sakrejda]

For now I think we can do this locally. In general I do make test before I commit anything to develop and adding cpplint to that workflow sounds useful. CI seems like too much infrastructure for now (?)

• [x] Add cpplint on all hand-coded cpp files to makefile (maybe "make test" for cpplint + gtest, "make gtest" for the c++ tests and "make lint" for cpplint(?)
• [x] Grab/use Stan's options for running cpplint---there was a discussion about this on stan-dev and Daniel listed the options that run on Stan. They're also in the code.

[sakrejda]

cpplint tests passed locally and on travis, closing, I'll wait to merge till the whole CI thing is done.