Set logger level to debug
Add more details to log when an event was received.
Log github's delivery guid and pass it with payload

We had a problem with some of the github events and we're not sure
what's going on. @github suggested to keep delivery guid and event type
somewhere, so they can inspect the requests easier.
Merge branch 'master' into mm-improve-logging

Conflicts:
	lib/travis/listener/app.rb
Enable debug temporarily.
Fix logged details for pull requests.
Log only 7 char shas.
Log head commit and commit ids properly for push.
Fix log payload.
Bump log level back to info.
Merge pull request #9 from travis-ci/mm-improve-logging

Improve logging
Handle missing head_commit, only handle push/pull_request events.
Split up log line for easier error location.
Ignore Sinatra::NotFound exceptions.
Ignore logs.
Change k/v logging to use maps.

Makes the code just a tad more readable.
It's delivery_guid, not delivery_guide.
Log payload and error when logging event failed.
Log error in the right place, handle gracefully.
Handle missing head repo gracefully.

The payload for closed pull requests doesn't include that currently.