Make python code collapsible:

- Remove unused code: https://github.com/getpelican/pelican-plugins/issues/140
- Add javascript and CSS to header to toggle code areas
- load jinja2 template from file
add jinja2 template file to have collapsible python code
Merge branch 'master' into collapse-code
remove unnessecary replace from template, require white space after hash
get jquery via https from google's cdn
Maintain backward compatibility by not requiring that pelicanhtml is copied to the blog home
Explain new collapsible code cells feature in Readme.md
attempt to merge master with collapsible code
work with IPython 1.x and 2.0
Update Readme to specify which template is needed for which IPython version
Merge pull request #153 from joergdietrich/collapse-code

Collapsible notebook code cells in liquid_tags plugin