Changed the formatting of the comment on the 64-bit OS X version
Added a placeholder for the extra download information
Defined about-download to make future refactoring easier
Changed about-download to an ID

This allows it to work with jQuery selection without any possible
conflicts
Added a line for setting information in the download box
Added code to modify the download button

Human-readable languages appear in the download button along with the OS
Made default phrasing clearer
Cleaned up formatting