Fix Website files and add deploy task in grunt

Website is now functional:

- Fix image switch functionality
- add grunt deploy task to handle deploying to gh-pages

For testing reference: http://lwhiteley.github.io/angular-image-zoom/

After merge just run 

`grunt deploy`

Should resolve issue #4 

### Grunt deploy

This task creates a temporary website directory by copying the `dist` folder into the `demo` folder.
The task then commits the `demo` folder to the `gh-pages` branch to be deployed for viewing.

`demo/dist` is ignored by source control so no need to worry about duplication