Uses uglify's drop_console option in the production config.

I thought about using compress_js, but I wasn't sure the intent of that. Fix for #93.
Ref: http://stackoverflow.com/questions/20092466/can-uglify-js-remove-the-console-log-statements
Merge pull request #94 from optimizely/ccorda/remove-console-production

Uses uglify's drop_console option in the production config.