lml/ost#347: Integrate unconfirm gem.

- Add gem dependency.
- Add configuration file for unconfirm.
- Include JS and HTML.
- Add migrations.
- Modify free response and multiple choice submissions
  to use unconfirm.
I did not.  @Dantemss, can you take a look sometime in the coming weeks?

My inclination is to take it on faith now, subject to Kim's manual testing, and let us interact with it a bit in OST.  Then when we integrate unconfirm into future products I'll definitely take a closer look.

Thanks for adding this functionality.

On Jun 27, 2014, at 8:48 PM, Lakshmi <notifications@github.com> wrote:

> In Gemfile:
> 
> > @@ -59,6 +59,8 @@ gem 'remotipart', '~> 1.0'
> >  gem 'babbler', '~> 1.0.0'
> >  gem 'sketchily', '~> 1.5.0'
> >  
> > +gem 'unconfirm', path: '../unconfirm'
> @jpslav - did you get a chance to take a look at the gem code?
> 
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