Added imagick extension

(Disclaimer: I'm very new to puppet policies and the like, very open to suggestions for improvement)

Depends on the `boxen/puppet-imagemagick` repo. 

I've tested it with php-5.3.3 and imagick-3.0.0RC1 and it seems to work well, (although I needed to refresh php-fpm, is this something the extension should do?). I used the APC extension as a base so not a lot needed changing.