readme: Resolve redirects, correct urls, use HTTPS

* Travis: Update code to the new standard.  (Move away from the odl "secure" domain, and using
  SVG for which looks better on HiDPI/Retina displays.)
* David: Update code to the new standard.
* Karma: Consistently link to v0.12 documentation.
* GitHub.io: Opt-in HTTPS.
* YouTube: Opt-in HTTPS.
* Angular: Redirect (https).
* Twitter: Redirect (https).
* Google Code: Redirect (https).