[PR-52] Build fails on RHEL 6.6.

Original issue is with: https://github.com/imagemin/gifsicle-bin/issues/36
 This is a GLIBC version error used by the native gifsicle package. Tracking down the dependencies gifsicle is used by grunt-contrib-imagemin which  is used my ngmin which gives us app minification. So I just removed everything related to app minification.