Restangular: Generic method overloads for get<T>(), getList<T>() and post<T>()

These changes made it easier for me to use restangular.

Simple example below:

    class Account {
        name: string;
    }
    interface IIndexScope extends ng.IScope {
        accounts: Account[];
    }
    [...]
    $scope.accounts = Restangular.all('api/accounts').getList<Account>().$object;