User management implementation etc.

* User management
    * User registration / authentication
    * Registration confirmation (via email)
    * Request contributor access
    * Grant contributor access (via email)
* Upgrade to the latest Django stable (1.6.3)
* Remove hard-coded settings and import them from another file not checked into version control
* A script to test CRUD on Sample, Subsample, and ChemicalAnalyses
* "public" resources (GET) should be accessible without API key authentication