Update bsSwitch.js to solve grunt uglify issue

I used your bootstrap-switch directive in dev mode (non minified) and everything works.
When I tried to use it in a distribution way after uglifying my directive.js file with grunt, I got an mangle issue.
I found a solution to this problem [here] (https://stackoverflow.com/questions/21688681/unknown-provider-aprovider-a-how-do-i-find-the-original-provider/21787020#21787020?s=c465fa0149184c988f2dee0e1d9ba7c9).