Speedup rvm ruby on mac

If you are using rvm you may have encountered some performance issue with ruby. For some detailed information of the root source have a look at https://github.com/wayneeseguin/rvm/issues/1240.
To fix this issue follow along these simple steps.

1. Update RVM to latest stable

   rvm get stable

2. If you have XCode 4.3 installed make sure automake is installed

   brew install automake

3. Reinstall ruby with rvm (example)

   rvm reinstall ruby-1.9.3-p286

That's it!