Updated beginner's fitness guide

I've updated the beginner's fitness guide. Changes include:

-Link to newer/more complete version of "Starting Strength" workout
-Link to newer/more complete version of "Stripped 5x5" workout
-Expanded nutritional supplement section with more links to supporting research

I'll update the sidebar links soon, for now you can get it directly here. The .pdf version will actually have working links now. :)