Handler tests.

Separated database access into a service so that handlers can be tested
with a mock database simplifying unit testing.

Also had to modifed handlers to pass URL variables directly into them
instead of attempting to mock a request, because mocking gorilla/mux's
Var function was difficult.

Used suggestion from :
https://groups.google.com/d/msg/golang-nuts/Xs-Ho1feGyg/iAeo5HdeFlwJ