Remove lang mapping for Haskell.

Also adds customized options for the worker for the queue name
and the number of vms per worker process.
Bump cookbook version for travis_worker
Updated the changelog
Fix a syntax error in the phantomjs cookbook.
Add support for PHP 5.4.25 and 5.5.9.
Add support for PHP 5.6.0alpha1.

Fixes travis-ci/travis-ci#1886 and #268.
Install haskell-platform-doc

Addresses https://github.com/travis-ci/travis-ci/issues/1351