Loading spinner added for inline reply

Now when posting a comment (through Inline Reply box) there is an indication of progress. The 'Cancel' button disappears, the text of the reply button changes to 'Posting...' and a small animated loading spinner appears to the right of the reply button to indicate progress. This should cause less confusion for those using inline reply.

Note: sorry about the double pull request, there was a mixup with your promo image the first time, merge tool didn't handle images properly I guess.