Introduce one-time binding in style-guide?

[sh-waqar]

The normal approach for data-binding in angular is by using {{vm.foobar}} this introduce a two-way binded variable and angular initiates a $watcher. After Angular 1.3 there is a way to reduce this $watcher and in case where only one-time binding is needed {{::vm.foobar}} syntax can be used.

This will help reduce number of $watchers and increase performance.

[johnpapa]

good idea. any community members want to make a PR?