Remove 'coala' from COMMIT_AUTHOR_EMAIL

[jayvdb]

.travis.yml currently sets COMMIT_AUTHOR_EMAIL: "nobody@coala.io" , but that violates this repositories rule that 'coala' shouldnt be mentioned anywhere.

One approach is to use a generic email address.
Another is to use the git remote info to find the GitHub org (#26), and then derive an email address from the GitHub org.

[andrewda]

I think the best we can do here w/o making a GitHub API call is to do something like nobody@{org}.com, but it might not be the best idea to try and guess the org domain if we're going to be wrong 90% of the time. It's probably better to use something like ghost@github.com or {org}@example.com.

[nalinbhardwaj]

@jayvdb this was closed in PR #27 only partially(since the email change was out of scope there). Should I make another PR just changing the email to something generic like CI@travis.com, or something like @andrewda suggested..