Fix Website files and add deploy task in grunt

[lwhiteley]

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