NEW: Added Travis CI widget.

Requires the following environment variables:
* TRAVIS_AUTH_TOKEN_PRO (for private repos)
* TRAVIS_AUTH_TOKEN_ORG (for public repos)
* TRAVIS_REPOS_PRO (comma-separated owner/repo names)
* TRAVIS_REPOS_ORG (comma-separated owner/repo names)
QUALITY: Removed ssil-tv.erb.orig and added rule to .gitignore.