Added computed property keys to object literal enhancements

https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object-initialiser
http://wiki.ecmascript.org/doku.php?id=harmony:object_literals#object_literal_computed_property_keys
Reindenting Enhanced Object Literals section because of the syntax highlighter glitch

Syntax highlighter has a glitch/bug, which causes the computed property name section to be hidden completely. Bug doesn't seem to apply when using four-space indentation.

Regarding the highlighter issue, filed bug report:
https://github.com/tmm1/pygments.rb/issues/115
Merge pull request #35 from flaki/master

Added ComputedPropertyNames feature