(Homebrew wiki) troubleshoot sections in each distro now refer to common page

[Isaac Saito]

Hi ROS applecation developers,

I noticed the troubleshooting section in each installation page are disjointedly maintained, resulting in some useful info added to a particular version are missing in the other pages.

For Homebrew, I merged and separated the entire troubleshoot section.

http://wiki.ros.org/os/OSX/Homebrew/troubleshooting

Hydro and Groovy pages are now referring to it.

http://wiki.ros.org/action/info/hydro/Installation/OSX/Homebrew/Source?action=diff&rev2=14&rev1=13
http://wiki.ros.org/action/info/groovy/Installation/OSX/Homebrew/Source?action=diff&rev2=72&rev1=71

So far it looks good to me, but if these changes innovate problems, please don't hesitate to modify / revert.

--Isaac