[#721] Removed old references to instance methods

modules/timeline-sources/popcorn.timeline-sources.unit.js

@@ -50,8 +50,7 @@
     expect( 3 );
 
     var count = 0,
-        p = Popcorn.getInstanceById( "video" )
-        .volume( 0 );
+        p = Popcorn.instances[ 0 ].volume( 0 );
 
     function plus() {
       if ( ++count === 3 ) {