md-tabs: a lot of watchers generated

[tedbeer]

md-tabs component creates a lot of watchers on window resize when it's hidden.
Material v0.7.1 and v0.8.0-rc1-master-ffbea7d
All browsers are affected.
Test: http://codepen.io/tedbeer/pen/bNvMmw
The test uses ng-stats to show number of watchers. You can also inspect $$watchers in the md-tabs scope to see it's growing.

Proposed fix:

*** /MaterialDesign/src/components/tabs/js/paginationDirective.js
***************
*** 65,73 ****
        onTabFocus(newTab);
      }

      function updatePagination() {
        if (!element.prop('offsetParent')) {
!         var watcher = waitForVisible();
          return;
        }

--- 65,74 ----
        onTabFocus(newTab);
      }

+     var watcher = null;
      function updatePagination() {
        if (!element.prop('offsetParent')) {
!         watcher = waitForVisible();
          return;
        }