add rmagic gem

* adding ImageMagic and rmagic
*
* download and installation
* $ path=c:\RailsInstaller\ImageMagick-6.8.3-Q16;%path%
* $ gem install rmagick --
'--with-opt-dir="C:\RailsInstaller\ImageMagick-6.8.3-Q16"'
* SET PATH=c:\RailsInstaller\ImageMagick-6.8.3-Q16;...
* add rmagic gem