Defer getting file contents until needed

This will avoid calling the API to get file contents from GitHub as the
`CommitFile` object is constructed. Also, allows us to avoid getting contents if
file is removed.

* introduce `Commit` class responsible for specific commit
Guard against decoding nil file content

Causes this error: https://app.getsentry.com/app20126465herokucom/production/group/26845983/
You get reviewed by Hound
Disable Skip cop
Provide email address to Intercom
Guard if cotents of the file are nil
Guard about potentially missing data from GitHub

Addresses:
https://app.getsentry.com/app20126465herokucom/production/group/18572350/
Bump Ruby version to 2.1.2

https://github.com/thoughtbot/hound/issues/334
Show payment dialog when activating a private repo
Create subscription when payment is received
Remove dialog
Show price on payment form
Test against serializer
Create Stripe subscription with the correct plan type
Activate repo when Stripe subscription is created
Remove jQuery
Change email job to have high priority
Clear repos if any are missing information

* This will trigger a forced refresh and fill in missing in_organization
* and private fields.
Simplify SubscriptionsController
Add RepoSubscriber to handle Stripe and Repo subscriptions