Update hide_input_all extension

- add wiki images
- hide cells on reload
Merge pull request #67 from juhasch/add_links

Add links
Merge pull request #68 from juhasch/hide_input

Update hide_input_all extension
Fixed zen background url.
Add support for changing of the level of heading cells.
Fixed path.
Merge pull request #70 from bjanssen/master

Add support for changing of the level of heading cells in the hierarchical collapse extension.
Merge pull request #69 from ipython-contrib/fixzen

Fixed zen background url.
Add metadata and a visual indicator to newly created HeadingCells. Fix minor bugs.
Merge pull request #71 from bjanssen/master

Add metadata and a visual indicator to newly created HeadingCells.
Fix double click-edit bug.
Update link to css so collapsed indicators will be shown.
Fix non-responsive collapsed section indicator bug.
Merge remote-tracking branch 'upstream/master'
Merge pull request #73 from bjanssen/master

Fix double click-edit bug.
Merge remote-tracking branch 'upstream/master'