start using saved market data rather than making new calls
grab exchange data from rethink
finish api methods
Merge branch 'master' into enhancement/use-markets-stored-in-rethink

Conflicts:
	app/models/coin.rb
fix failing tests
Merge pull request #2 from mculp/enhancement/use-markets-stored-in-rethink

Use the market data we've stored in rethinkDB instead of making on-demand API calls