Add autosaving to the notebook, while retaining manual checkpoint creation.
Autosave will perodically save the notebook, with a default interval of two minutes. This interval is configurable, and the system will automatically back off the frequency if it detects that the save operation takes too long. This can be the case if working remotely over a slow link, so this will automatically conserve bandwidth.
The manual save operation remains available and bound to the same keys, but now it causes the creation of a separate checkpoint, which is stored in a hidden directory called `.ipynb_checkpoints`. This provides users a poor-man's version control with a single revert point and the ability to safely experiment with potentially destructive changes to a notebook without concern that the autosave operation may clobber their file on disk.
See [IPEP 15](https://github.com/ipython/ipython/wiki/IPEP-15%3A-Autosaving-the-IPython-Notebook) for details of the proposal.
autosave interval is tuned based on the duration of saves.
Autosave will never happen more frequently than every 30 seconds,
and if saves take more than 3 seconds, autosave will fire every 10x the duration of the save (i.e. if save takes 6 seconds, it will be every 60 seconds, etc.)
Update to CodeMirror 3 and start to ship our components
The main purpose of this branch is the update to CodeMirror 3 and ship it as a bower component. Because CodeMirror doesn't use proper semantic version tags, we have created a CodeMirror ipython fork. The sole purpose of this fork is for us to maintain properly named tags that bower can install from.
As a side effect of these changes, we are now shipping in place all bower components that we are using (bootstrap, less. codemirror, jquery). BUT, the version of jquery in components is not yet being used as we are still stuck with the old version attached to the nasty jquery.ui branch we ship. In a later PR, we will need to get rid of that jquery.ui branch (replace those capabilties with bootstrap) and then move to a stable version of jquery.ui that matches that of the jquery component depended upon by bootstrap.
Brian E. Granger
MinRK
Fernando Perez