Update custom.js example

- Use IPython.load_extensions
- Assume all extensions reside in `nbextensions`
Update runtools

- use new icon naming scheme
- update to require.js
Update navigation-hotekys extension

- fix ctrl+y
- change shift/ctrl-enter behavior to just go into edit mode after
execution
Make custom.example.js run in IPython 2
Update custom.example.js
Use app_initialized.NotebookApp
Make example custom.js work for 2.x branch
Merge pull request #95 from juhasch/2.x

Make custom.example.js work for IPython 2.x