Add CoffeeScript support

* Use [CoffeeLint] to keep to a community-supported open source standard.
* Roll out CoffeeScript to certain GitHub orgs.
* Memoize the HTTP requests.

[CoffeeLint]: http://www.coffeelint.org/
Add flag to enable CoffeeScript

* rename `Null` style guide to `Unsupported`
Handle error where Services team already exists

Error reference:
https://app.getsentry.com/app20126465herokucom/production/group/18233199
Don't check for line presence in the latest commit

This fixes an issue that Hound wound't comment when multiple commits got pushed
to a PR at the same time. As it was, Hound would check if only the head commit
included the line with violation -- resulting in no comment if the violation
came in the previous commit.

Instead, simply check if the violation on the line was previously unreported.
Add account page

* show repo totals
* show a list of billed repos
* refactor external customer data fetching to `PaymentGatewayCustomer`

https://trello.com/c/6AyMCv1t