Adding a `getFirst` method to restangularStorage

It allows to get back the first n result of a query only (instead of the complete list)
For instance, if you want to get back only the last message.
Adding a `copy` method to restangularStorage
Fix getFirst function
Replace element.clone with restangular.copy(element)
[Generating dist files]
Merge pull request #47 from Evaneos/restangular-storage-improvement

Restangular storage improvement