Make db module take optional config key param
Make badge module take optional config key param
Make tests use TEST_DATABASE from config
Update README with test database config info
Make config key required in db and badge modules
Merge pull request #49 from stenington/configurable-db

Separate db for testing
To ensure that configurtion can be pulled identically from config files, the ENV, and
command-line arguments, the db module no longer relies on pulling config objects
with config-store (which only works for file-based config).
Merge pull request #55 from stenington/52-dont-use-config-objects

Make DB config work the same everywhere