fix(tooltip): incorrect position when text wraps

The $digest that was removed in 32c470 is actually necessary to get the
tooltip contents rendered. The rendered content is important when the
tooltip is on the right edge. See Plunker in #2995:
http://plnkr.co/edit/8GZ5F5zj3Xe6IinXQz74?p=preview

Reverts change in 32c470 (#2995) but fixes it in another way.

Fixes #2995
Fixes #2992
Fixes #2951
Closes #2996