change underlying data format from json to csv; ALSO implemented dynamic formatting methods for model
fixed very silly error naming csv files .json
changed name of testing env var to CCJ_TESTING
Merge branch 'v2.0-dev' of https://github.com/sc3/cookcountyjail into v2.0-dev

Conflicts:
	ccj/models/daily_population_changes.py
Merge pull request #190 from bepetersn/v2.0-dev

v2.0-dev -- fixed naming issue leftover from using json as backend for DPC model