Update ACE Editor to version 1.2.9

The new ACE editor introduces full support for emojis (and, thereby, UTF-16 characters with high- and low-surrogates). Hence, we can remove our custom fix.

Further, this update will allow emojis to be used in pair programming sessions.

vendor/assets/javascripts/ace/ext-themelist.js

@@ -22,6 +22,8 @@ var themeData = [
     ["Chaos"                ,"chaos"                   ,  "dark"],
     ["Clouds Midnight"      ,"clouds_midnight"         ,  "dark"],
     ["Cobalt"               ,"cobalt"                  ,  "dark"],
+    ["Gruvbox"              ,"gruvbox"                 ,  "dark"],
+    ["Green on Black"       ,"gob"                     ,  "dark"],
     ["idle Fingers"         ,"idle_fingers"            ,  "dark"],
     ["krTheme"              ,"kr_theme"                ,  "dark"],
     ["Merbivore"            ,"merbivore"               ,  "dark"],