fix(carousel): #488 Carousel fails to update model changes.

Fixed carousel to update the carousels isolate scope when a slides ng-repeat $index has changed e.g. with orderBy filter.

Created new PR due to fix being made to outdated version in PR #1969. However, I would like to continue the discussion of the issue brought up about using $index by @chrisirhc and users not using the ng-repeat directive for their slides. My question was, due to the fact that users are managing their slides manually, should there be an expectation for updates to these slides to affect the order in the carousel after initialization? If that is a valid expectation, what would be the best method for watching for these changes? e.g. a watcher on the entire carousel DOM.