Add flowdock notification support

Adds two configuration variables that enables sending notifications to a flowdock flow.
Allow generic REDIS_PROVIDER env var

Setting REDIS_PROVIDER to the name of the env var that has your redis
URL will use that URL. So for example, if your provider is OpenRedis,
you'd want:

    REDIS_PROVIDER=OPENREDIS_URL
    OPENREDIS_URL=redis://...

Same for any other provider. Closes #51.
Add a fabric provider

Adds a fabric provider based on the capistrano provider. Allows for
custom fabric command format via a DEPLOY_COMMAND_FORMAT.
Merge pull request #52 from kiratalent/add-flowdock-notifier

Add flowdock notification support
Merge pull request #53 from foca/redis-provider

Allow generic REDIS_PROVIDER env var
Merge pull request #54 from kiratalent/fabric-provider

Add a fabric provider
break long line out to a method
version buuump
remove debugger and downgrade simplecov
update docs to reflect new services and providers
Merge remote-tracking branch 'upstream/master'