Merge pull request #2 from alphagov/update_db_config

Change how db auth is done for dev and test.
Failing tests for path reservation
Add factory_girl
Add Reservation model
Refine json representation of Reservation
Disable Rails’ automatic JSON parsing.

Causes problems - see comment on disable_params_parser.rb for details.
Implement reservation put action.

This doesn’t yet check for conflicts, but it does cover all the other cases.
Prevent reserving path claimed by another app.