Fix tests to look for http:// git gem rather than git://

I couldn't get the git:// urls to work in my firewalled enterprise that requires an http proxy. This PR changes the git:// url to http so that it can work through a proxy.

This change is testing essentially the same thing as the git:// use case but with http instead. Arguably a super set of the git:// test.

This change updates the ruby spec to look for an http:// url instead of git://

The assets PR can be found here: https://github.com/cloudfoundry/vcap-test-assets/pull/6