Create a NewsletterSubscription form object

* Add routes for newsletter subscription
* Update partial
Use partial in all the places
Add VCR and webmock
Merge with upstream changes
Add Newsletter Service
VCR the feature spec
Better newsletter params
Move list to env
Capture signup exceptions
Upgrade raven/sentry
Send exceptions to sentry
This didn’t work well. Reverting
Use fetch to get newletter params
Merge pull request #121 from gaslight/newsletter

Newsletter Service
Merge remote-tracking branch 'production/master'

* production/master:
  Use fetch to get newletter params
  This didn’t work well. Reverting
  Send exceptions to sentry
  Upgrade raven/sentry
  Capture signup exceptions
  Move list to env
  Better newsletter params
  VCR the feature spec
  Add Newsletter Service
  Merge with upstream changes
  Add VCR and webmock
  Use partial in all the places
  Create a NewsletterSubscription form object