Add links to "travis ci" to README file.

Linking branches "master" and "1.9" for now.
Travis CI: trying to make the build more "resilient".

Related to issue #11880.
Travis CI: Adding comments to ".travis.yml".

Related to issue #11880
Fix for crash bug caused by Iframe NULL reference

https://github.com/ariya/phantomjs/issues/10947
https://github.com/ariya/phantomjs/issues/11103
https://github.com/ariya/phantomjs/pull/11984
Add example for how to post a json request to HTTP server

https://github.com/ariya/phantomjs/issues/11969
Merge branch 'master' of https://github.com/ariya/phantomjs