Fix template layout

The body variable at Pandoc template **must** not be indented
because the indentation will propagate into the HTML.

Example:

    $ cat page.html
    <!DOCTYPE html>
    <html>
      <body>
        $body$
      </body>
    </html>
    $ pandoc -s -t html --template=page -o sample.html sample.md
    $ cat sample.html
    <!DOCTYPE html>
    <html>
      <body>
        <pre><code>def foo():
            return None</code></pre>
      </body>
    </html>

Solution:

    $ cat fix.html
    <!DOCTYPE html>
    <html>
      <body>
    $body$
      </body>
    </html>
    $ pandoc -s -t html --template=fix -o sample-fix.html sample.md
    $ cat sample-fix.html
    <!DOCTYPE html>
    <html>
      <body>
    <pre><code>def foo():
        return None</code></pre>
      </body>
    </html>
Breaking instructions into pieces and explaining labels
Putting link to layout instructions in the first paragraph
Merge pull request #33 from gvwilson/gh-pages

Building validator for lesson contents
Changing names based on feedback from @willingc
Merge pull request #30 from r-gaia-cs/fix-code-indetation

Fix template layout
making python script runnable for pandoc
added shebang to the python pandoc script
Merge pull request #36 from twitwi/make-python-script-runnable-for-pandoc

making python script runnable for pandoc
remove .prereq from readme
trigger prereqs class with title

Previously, Div creation was triggered by a Blockquote that began with a
header that contained a single class that was in a list of special
classes.

Now, Div creation is *also* triggered by a Blockquote that begins with a
header that has it's text contained in a list of special titles. The
title is used to lookup an appropriate class to give the Div.

In particular, 'prerequesites' is a special title, giving the class
'prereq'.

This input:

    > ## Prerequesites
    >
    > A short paragraph describing what learners need to know before
    > tackling this lesson.

will trigger this output:

    <div id="prerequisites" class="prereq">
    <h2>Prerequisites</h2>
    <p>A short paragraph describing what learners need to know before
    tackling this lesson.</p>
    </div>
Small improve at tools/blockquote2div.py

- Use UPPERCASE for global constants
- Add Learning Objectives to SPECIAL_TITLES
- Fix samples
clarify documentation, make all classes special

This means that you can trigger div creation by

1. Using a special title
2. Using a special class on an arbitrary title
Merge pull request #37 from aaren/prereq-divs

Prereq divs
Merging with gh-pages
Merge pull request #31 from gvwilson/splitting-lesson-instructions

Splitting lesson instructions