Adds sharded data source.
WIP changing aggregating data source to use urlopen, parse URLs correctly.
Rid of debuginfo, fix list_sources
Adds documentation to the aggregating data source, removes title and legend methods.
Merge branch 'develop' of github.com:Yelp/firefly into sharded_data_sources
Gives Firefly its first unit tests. Only covers the new AggregatingDataSource for now.
DRYs up tests a bit
Merge pull request #52 from fhats/sharded_data_sources

Sharded data sources