rename cbgUtil to bgUtil and instantiate it separately with cbg data and smbg data in tidelinedata
display changes for smbg fallback
address feedback from PR:
- more informative error message when BGUtil not given a DAILY_MIN in the opts
- return bg data type along with `breakdown` object to make it easier to switch puddle labels
add tests
Merge branch 'master' into jebeck/smbg-fallback
more PR feedback (mostly minor refactoring)
only use strings as object keys where absolutely necessary
oops...set up stats pool properly for two-week view with smbg instance of BGUtil
Merge pull request #101 from tidepool-org/jebeck/smbg-fallback

setting up fallback to smbg stats when not enough cbg data