Remove vendor/cache

[memk]

Hello there, GitHub.

Built-in cache now available on Travis when using sudo: false. Should simplify codebase and speed up build.

I do hope you like, @gjtorikian @benbalter @github

[memk]

no Travis?? but there is a travis file.

[benbalter]

@memk Thanks for this. With apologies, I didn't see this and implemented the same via #20. The cached Gems was an artifact of our internal CI process, from when the Gem was initially under development. Either way, thanks for the pull request.