Fixed final complete callback not firing in angular 1.3

In latest angular 1.3 $animate.leave returns a promise and does not accept a callback anymore.
Changes are backwards compatible with 1.2.

Not sure what to do with tests. After quick glance at karma docs I don't think it is possible to make 2 different file inclusion cases to test against 1.2 and 1.3, so with this change coverage is down to 99.12%.

Kind of depends on #101 or #99 being accepted first, I will update pull request if one of those is accepted.
(relic-@818c673d8feb9ad410e63f98b3a3e35c55fa7a52 has  #101 applied)