Fixes transclusion on angular v1.2.18+

The choices template needed `ng-tranclude`, but it won't work anymore the same way since angular changed/corrected the way the transclusion and the scope bound.

The alternative could be to use a new class `ui-select-choices-row-inner` instead of `ng-transclude` to mark the location where we want to put the transcluded content by calling the transcludeFn from link function.

Working [plunker](http://plnkr.co/edit/TDmWk1gomDjDWrQggEXm?p=preview)

Fixes: https://github.com/angular-ui/ui-select/issues/85
Fixes: https://github.com/angular-ui/ui-select/issues/80