Add beautify output

[the-glima]

Example: https://github.com/frontendfriends/gulp-combine-mq#usage

[ghost]

this would be very helpful... I actually switched to using 'gulp-combine-mq' for this reason. The problem is that 'gulp-combine-mq' doesn't have a "log" feature which was very helpful to see which media queries were being affected in my build.