Add in_testing config option to Nominatum

Checking against Rails.env.test? fails on Travis.
Remove nominatum.rb's dependence on Rails

The user_agent and user_agent_email are now set as class instance
variables in config/initializers/nominatim.rb.
Replace string keys with symbols in Nominatim spec.

We're using symbol keys in the actual code, and hence should probably
use test data of the same format.