WIP on text selection: selection directive works

The selection directive now works correctly with the HTML content
of a text. I had to take the functionality of ng-bind-html-unsafe
and merge it into the directive itself to make it work, so as it
currently stands the directive isn't really suitable for a generic
UI library. It may be possible to separate out the functionality
of the selection directive from the HTML content, making it more
suited for generic use -- but since I've tried several approaches
and this is the first one that's worked, I'm going to go with
this one until I figure out how to separate the concerns properly.

Note that currently, we're not doing anything with the selected
text except logging it to the Javascript console. Next step is to
actually do something with it: copy it into the answer box, mark
a yellow highlight in the selected part of the text, etc.
Add rangy library (MIT license)

Rangy is a cross-platform library for managing text ranges, selections,
and so on, which can also apply a highlight to any range, automatically
adding the appropriate <span> elements where needed. We'll be using it
for the text-highlighting feature on the question page.

The version checked in here is the latest currently available, 1.3a772,
released in February 2013. I chose the 1.3 alpha release instead of the
stable 1.2 release because rangy's highlighter module is new in 1.3.
Text selection now works properly

Several changes in this commit, which go together as a logical unit:
  * Moved new-answer edit control to top of question pane
  * Added "scripture-quote" CSS style
  * When user highlights a section of text, it will show up in the
    question pane in "scripture-quote" style
  * When answers have a (non-blank, non-null) textHighlight value,
    the selected portion of Scripture will also show up above the
    answer, again in "scripture-quote" style
Breadcrumbs
Merge remote-tracking branch 'origin/feature/textselection'