Improve speed of tests.

Installed the vcr gem which stubs out all Net::HTTP requests unless they
are explicitly allowed. =)
Merge pull request #620 from loomio/improve-test-speed

Improve speed of tests
Merge branch 'master' of github.com:loomio/loomio into refactor/discussion-controller

* 'master' of github.com:loomio/loomio:
  Improve speed of tests.