Adds @sashax, /developer.html, and webmaster verification

Merges #88, #116, and https://github.com/18F/18f.gsa.gov/commit/bbf2fce689647be9568099272a06e90914fda90c into `master` for deployment.

All of them can be seen on staging:

* https://18f.github.io/18f-staging/
* https://18f.github.io/18f-staging/developer.html
* https://18f.github.io/18f-staging/googleaaa373e99c6c59e3.html