Change phrase for check-in to "check in with foursquare". Fixes #7.

I agree with @joshmtucker in #7. According to the Voice Command Checklist[1] voice commands should:
* Has an imperative verb with an object
* Refers to Glass as the subject carrying out the action

I changed the phrase to the proposal of @joshmtucker: OK, glass "check in with foursquare"

[1]: https://developers.google.com/glass/distribute/voice-checklist