Fix double slashes

One slash too many in the url path
Add check to folding preprocessor

Only do folding when there is metadata info.
help_panel uses quickhelp

Change help_panel extension to use quickhelp function to generate help
text
Improve help-panel display

Make fonts smaller and circumvent IPython bug in quickhelp
Fix registering codemirror notification

Dynamically add codemirror change notification handling, so spell
checking also works for newly created or redefined cells.
Merge pull request #52 from juhasch/master

Improve help_panel to use quickhelp