add "main" property to package.json so can use with npm + browserify

[focusaurus]

I think if you just add a main property pointing to the truncate.js file browserify users will be able to use this package via npm without needing bower, which would be nice.

[BernardoSilva]

@focusaurus The property can be found on package.json.

If you're interested a supported fork can be found here

I created a PR based on this ticket to add some documentation: https://github.com/BernardoSilva/angular-truncate/pull/8