Prevent playback controls from hiding while the user is scrubbing

Fixes #64

renderer/views/player.js

@@ -117,6 +117,7 @@ function renderPlayerControls (state, dispatch) {
 
   // Handles a click or drag to scrub (jump to another position in the video)
   function handleScrub (e) {
+    dispatch('videoMouseMoved')
     var windowWidth = document.querySelector('body').clientWidth
     var fraction = e.clientX / windowWidth
     var position = fraction * state.video.duration /* seconds */