Add Godep support and hook up Travis CI

Added dependency vendoring with `godep`.  Renamed imports from `googlecloudplatform` to `GoogleCloudPlatform` to fix `godep` cross-platform support.

Added Continuous Integration testing with [Travis CI](https://travis-ci.org/GoogleCloudPlatform/gcloud).  Currently Travis tests against Go 1.2, 1.3, and 1.4.  Do we want to support all the way back to 1.0?

[![Build Status](https://travis-ci.org/GoogleCloudPlatform/gcloud.svg?branch=build)](https://travis-ci.org/GoogleCloudPlatform/gcloud) woot!