append to body option

[Vandivier]

This lib suffers the same issue identified in angular-ui ui-select issue #41

angular-ui/ui-select#41

The issue is that when the drop down crosses certain html boundaries the items in the list cannot be selected. For example, two ng-includes where a drop down inside the first crosses over one into the other. Z-index can't fix the problem. A hacky solution involves using position: fixed, but the real solution is to append the list to the outer document instead of to the clicked element.

angular-ui implemented a fix, check it out. Till then I'll be switching to their lib.