Updated Copyright
Removed mention of MySQL Cluster plugin in docs
Added XtraBackup to provider list.

It was recently discussed to remove providers from the documentation
since they are more confusing to the end-user. For now, I simply
updated the list to reflect more current implementations.
Clarrifications, Formatting, CSS
Indented version tags, CSS updates

Indented the version tags where they were being used to describe a particular
command or function in the config and overview documents. Also a few more
CSS updates, largely over <pre> tags - I thought the default didn't make it
obvious enough that it was source code and it was running into other sections.
Merge pull request #89 from m00dawg/master

Documentation: CSS Updates other formatting, grammatical changes