Log error when sending Campfire message fails.

The problem could potentially be related to secure environment
variables, which could cause strange hostnames to be used.

Only one way to find out.
Ignore address errors when sending email.

It's no use retrying and raising them as they're pretty much
unsolveable.
Ignore rejected recipient errors when sending email.
If commits are not present in a push event, build head_commit

When a branch is pushed with a HEAD commit, which already exists on
github, a push event will not contain commits info, so we nead to use
head_commit, in order to get commit info.
Update specs for new travis-support
Merge pull request #264 from travis-ci/ps-fix-building-existing-commits

If commits are not present in a push event, build head_commit
Add a type field to the webhooks payload.

Allows differentiating between pull requests and normal push builds.
Merge branch 'master' into mm-webhook-includes-build-type
Merge pull request #265 from travis-ci/mm-webhook-includes-build-type

Add a type field to the webhooks payload.
Merge branch 'master' into twitter