Allow custom source for google_auth_proxy binary

- Add attribute node[:google_auth_proxy][:source]
- Move installation of google_auth_proxy binary out of LWRP and into
  google_auth_proxy::default recipe
- Add test-kitchen tests and fixtures
Add tests for installing google_auth_proxy from url

- Add install::remote_s3 test to fixtures in order to test installing
  google_auth_proxy binary from a url
- Patch google_auth_proxy::default to correctly handle the remote_file
  resource and fail properly with an invalid url