Disable google analytics in development.

Has the side effect property of forcing all experiments to happen
under a single global identifier, so experiment data is also impacted
less in development.
momentum scrolling in modal
Merge pull request #52 from PRX/fix/momentum_scrolling

momentum scrolling in modal
Merge pull request #51 from PRX/fix/disable_analytics_in_development

Disable google analytics in development.
merge master