Added "only-watched-property" attribute to directive

added possibility to set an "only-watched-property" directive to the fullscreen directive, as going to fullscreen is not always desired when clicking on the element itself. Instead, *only* the watched property should trigger the fullscreen functionality.
Updated README for "only-watched-property" attribute
Added text input in index.html
Merge branch 'master' of https://github.com/sebastianoe/angular-fullscreen into test
minor fix on index.html
Merge branch 'test'
minor fix on index.html