Added bower.json

Tested install locally including running with
generator-angular-fullstack so the file is added to bower_components in
index.html and it works.

Did not publish to bower registry.

To test local install:
1. Clone repo to local
2. `npm install` to get Grunt for build
3. `grunt build` to generate `build` folder with both full and minified
files
4. Navigate to folder with desired project
5. run `bower install ng-socket-io
~/path/to/ng-socket-io/location/bower.json`