Switching to lxml
Convert `=&gt;` to the more semantic `&rarr;`.

`&rarr;` is defined in the HTML 4 spec [1]:

  <!ENTITY rarr CDATA "&#8594;" -- rightwards arrow, U+2192 ISOnum -->

Don't make these replacements in example Python code:

On Sun, Jan 06, 2013 at 05:47:00AM -0800, Greg Wilson wrote:
> On 2013-01-06 8:37 AM, W. Trevor King wrote:
> > On Sun, Jan 06, 2013 at 05:21:02AM -0800, Greg Wilson wrote:
> > > * Where '=>' appears as a string in a Python program to be printed,
> > > it should be left alone.
> >
> > Oops. Sloppy me not checking all my automatic replacements. How do
> > you feel about replacing the Python occurences with `\u2192'`?
>
> -1: I don't want us to have to explain Unicode escape sequences that
> early in the show.  If we could actually trust all the editors people
> use, and legacy tools like Cygwin's 'cat', to display non-7-bit
> characters correctly, I'd just put the ' →' directly in the source, but
> hey, I'd like a unicorn too...

[1]: http://www.w3.org/TR/html4/sgml/entities.html
Tidying up the switch to LXML
Merge branch 'change-xml-parser' of github.com:gvwilson/website into change-xml-parser
Starting to revise web material
Turning off auto-recovery
1. Made @jiffyclub's changes to bin/compile.py.
2. Fixed HTML errors reported by LXML/HTML5 parsing.
3. Fixed other bin/* scripts as well (so that HTML5 generation is correct).
4. Still getting one error reported for a <script> tag in bootcamps/index.html that I can't figure out.
Trying to push changes to 3_0 material
Fixing the ampersand problem (apparently)
Changing  to
Adding DOCTYPE to HTML examples (in early sections)
Adding some challenges
Converting database chapter to learning goals
Another set of exercises for the shell
Minor updates to HTML parsing
Merge branch 'master' of github.com:gvwilson/website into instructors-guide
Merge branch 'master' of github.com:swcarpentry/website into instructors-guide
Fixed typo in about/faq.html

students -> studies
Doing some more work on the shell chapter
Fixed unmatched HTML tags in bootcamps/office-hours.html