Add a section concerning preinstalled PHP extensions.
Review documentation for installing additional PHP extensions.
Add a section concerning custom PHP configuration.
Reorganize PHP documentation and add a section on our PHP installations.
Add a blog post on preinstalled PHP extensions.
Small corrections after proofreading.
Mention the one-line command to enable an extension in the blog post.
Specify that this new feature can cause build failures.
some small changes to the blog, most so I can thank Loic for his amazing work!
Merge branch 'master' of https://github.com/travis-ci/travis-ci.github.com
some minor changes to the top bit thanking loic