Added bower.json

I registered the package with `bower` so that people can more conveniently install it.

`bower install --save jquery-bigtext`

See: http://bob.yexley.net/creating-and-maintaining-your-own-bower-package/

The package is linked to `git://github.com/pztrick/jquery-bigtext` and when this pull request is merged we can update the bower registry to the original repo URL.