Update to 2012 Update 4, and install both x86 and x64 on 64bit machines

Hi Mark,
updated this package to the latest vcredist2012 available. Also changed the install script to install both editions on 64 bit Windows (similar to your vcredist2010 package), and updated nuspec links.
Nowdays moderation is enabled on chocolatey.org, which means that the .ps1 file has to follow certain rules. I have adapted it already.