Creating lesson on regular expressions

Main changes

* Added metacharacter discussion
* Added anchor operator discussion
* Added some text for MCQ at start and end of topic.


On Mon, Sep 08, 2014 at 06:37:17AM -0700, Greg Wilson wrote:
> >  ---
> > -We are currently updating our lessons
> > -to incorporate what we've learned from our learners
> > -in the last four years.
> > +These lessons incorporate what we've learned in the last four years.
> > +Please have a look at <a href="{{site.github_url}}/bc">our GitHub repository</a>
> > +for updates and to help us make them better.
> 
> Whoops - what's this change doing in this PR?  Can you please merge
> from 'master' and push to your branch again?

It might be easier to rebase on master, since that will let you
resolve any conflicts on a per-commit basis.  If you merge you have to
resolve all the conflicts at once ;).  If you haven't rebased before,
I'm happy to talk you through it (e.g. on #sciencelab at
irc.mozilla.org [1,2]).

[1]: https://wiki.mozilla.org/IRC
[2]: https://kiwiirc.com/client/irc.mozilla.org/sciencelab