Deletes unused js files and loads minified files for improved load time

Also, adds check to avoid js error (missing targetUrl's value would
throw a js error -controller.js)
Adds config file instructions
Merge pull request #108 from quiaro/master

Improves load time and adds config file instructions
Merge branch '2.3.x' of https://github.com/craftercms/social into 2.3.x