VP-282: Updating the known issues

Updated the known issues section of the README with some more issues that came up during release testing.

README.txt

@@ -89,9 +89,17 @@ Captions:
 Full Screen:
     VP-258: YouTube videos break in full screen mode
     VP-191: Implement fullscreen functionality for Opera and IE
+    VP-279: In IE8, invisible full screen button is tab focusable. Going full screen removes video player from tab order upon returning to normal mode.
 
 UIO Integration:
     VP-269: Transcript language is incorrect in the language drop down after specifying a language in UIO
     VP-88:  UIO inputs preferences not being correctly applied on load
     VP-280: Contrast styles don't apply to captions
     VP-107: Changing text size with UIO does not change Video Player size until refresh for Flash videos
+    VP-278: In IE8, focus appears on video player container, but activates UIO instead
+
+Playback:
+    VP-277: Pressing space on the video container does not start the video in IE9 and IE8.
+
+Scrubbing:
+    VP-284: In IE8, keyboard scrubbing stops working after attempting to scrub