[#5] Modified return values form event/1 function in elvis_webhook adn added error handling code.
[#5] Fixed badmatch error.
[#5] Fixed bug on function that checks the existence of a comment.
[#5] Added modules in application's metadata so that relx doesn't complain.
[#5] Added registered in application's metadata so that relx doesn't complain.
[#5] Added jiffy as an app dep.
[#5] More coherent return value ok -> not_exists.
Merge pull request #40 from inaka/jfacorro.5.github.integration.server.fixes

[#5] GitHub Integration: errors and bugs fixes