Send rewards directly to Btc, retain Coinbase as fallback

[ruuy]

Implementing idea from mailing list: https://lists.riseup.net/www/arc/whispersystems/2013-12/msg00009.html

Commit message: Users can specify a 'Send-Bitcoin-reward: '-line in the commit message, containing the address they want to get the payment delivered to. This will be used as default. In the case the line is not supplied, money is sent to coinbase e-mail.

[ruuy]

I wrote a git hook that appends a 'Send-Bitcoin-reward: '-line to every commit message. Is Readme file a good place to explain/publish it?

[ruuy]

oh sorry, will try to fix for passing tests.

[ruuy]

Added the hook to README.md.

[chrisglass]

Nice! Pretty cool feature.

[SkyzohKey]

This would need to be merged :p