Add dict key completion in IPCompleter
Additional test coverage for dict key completion
Containers resolve instances.

When a container has an instance traits, the instance's klass is
properly resolved when given as a string.
Remove extra action generation in "All Magics" menu population.

The function that populates "All Magics" and "CLASS magics" menus
used to create two separate QActions: one for the all-menu and one for class
menu. There is no apparent reason for doing that, since single QAction can
happily serve multiple menus and buttons.
allow async output on the most recent request

Keeps track of the most recent request, so async output is still allowed
schedule async flush

allows threadsafe flush from background threads
Added test
Add support for PyQt5.
log all failed ajax API requests
dialog on New Notebook failure
support use_cloudpickle in addition to use_dill
Removed whitespace changes
allow keyboard interrupt to break out of ipdb

@takluyver @minrk and I discussed this issue in person.

It's currently problematic that there is no way, short of restarting a
kernel, to get out of an ipdb session if you've deleted the output of
the cell in the notebook which started it (by e.g. re-executing that cell).

This patch makes Ctrl-C behave the same as Ctrl-D inside of ipdb - it
exits the ipdb session. This also makes it possible to stop ipdb
sessions from another client.

I polled @katyhuff, @scopatz, and some other pyne/pyne hackers and they
were surprised to hear that this was not the behavior already.
Comments and minor fixes
Make dict key completion more conservative

Only handle subtypes of dict, struct arrays and DataFrames
Safe isinstance for unloaded modules
add note about cloudpickle to whatsnew
fix delete_checkpoint errback name
Merge commit '55a3270aa4724bbea6a0ae0088f770c46aabf04a' into patch_2565_sidewindow
Introduce a doclkable widget that will substitute "all magics" menu.

Features:
a. filter by regexp
b. filter by class
c. double click pastes
d. push buttons to paste and run magics