Ignore .powrc for Pow.cx + RVM use.
Added liquid gem for templating.
Added support for testing web hook before repository has any commit history.
Merge branch 'empty-repo-test-webhook' into customizable-webhooks
Added `payload_template` attribute to WebHook. Added support for editing WebHooks. Added support for Liquid templates as WebHook request Payloads. Added WebHook payload syntax guide.