Merge branch 'develop_ribalba' into develop

* develop_ribalba: (24 commits)
  Fixed the tests so that the webhooks
  Removed more static files
  Added collectstatic to the build script
  Rewrite of the REST Webhook interface to run with celery in parallel and save the return codes of the webhooks. Also it retries 3 times if it fails.
  - Performance increase - Removed Google tracing -- Included external libraries
  cleared out all the static files
  Removed the iPhone style sliders for checkboxes.
  Skipping more tests
  more travis
  more testing
  More travis
  DB shouldn't be in git
  more travis
  Travis could tell me there is an error?
  test
  more travis
  Updated the travis file
  Trying to get all the tests to run
  Added the 50x.html file specified by the nginx config file but mysteriously missing from the repo
  remove mongo from before install
  ...
Merge branch 'develop' of https://github.com/eHealthAfrica/formhub into develop

* 'develop' of https://github.com/eHealthAfrica/formhub: