Allow Python-Code in Markdown Cells

Executes Python-code encapsulated in {{..}} in a markdown cell and
returns output.
Supports png, jpeg, latex and text output.
Move file
Example images
Update python-markdown

Save variables in metadata and show them after reload. Enables adding a
preprocessor for nbconvert, too.
Fix using old metadata entry

Use variables instead of cellhascode
Add markdown handling
Add text/html

Allow displaying html objects
Fix markdown handling

Marked will put text between `<p>...</p>`.
That is not desired, so remove.
Preprocessor for python code in markdown
Update to requirejs
Fix render on page reload
Merge pull request #83 from juhasch/py-markdown

Extension to allow Python Code in  Markdown