BDK 3.1 Launch

Updated BDK instructions page, update download page, and the blog post announcing version 3.0 to reflect the newest version (3.1).  Version 3.1 implements the reworking of scanning in C and the addition of features to improve stability when scanning for beacons.  
You can do **bold** text in markdown by surrounding the text in \*\*double stars\*\*