Ipykernel

- Use
[MPLBACKEND](http://matplotlib.org/devel/coding_guide.html?highlight=mplbackend#developing-a-new-backend)
environment variable to tell matplotlib >= 1.5 use use the inline
backend by default. This is only done if MPLBACKEND is not already
set and no backend has been explicitly loaded, so setting
`MPLBACKEND=Qt4Agg` or calling `%matplotlib notebook` or
`matplotlib.use('Agg')` will take precedence.
- Fixes for logging problems caused by 4.3, where logging could go to
the terminal instead of the notebook.
- Add `--sys-prefix` and `--profile` arguments to
`ipython kernel install`.
- Allow Comm (Widget) messages to be sent from background threads.
- Select inline matplotlib backend by default if `%matplotlib` magic
or `matplotlib.use()` are not called explicitly (for matplotlib >=
1.5).
- Fix some longstanding minor deviations from the message protocol
(missing status: ok in a few replies, connect_reply format).
- Remove calls to NoOpContext from IPython, deprecated in 5.0.

- Use a nonempty dummy session key for inprocess kernels to avoid
security warnings.

- Fix Windows Python 3.5 incompatibility caused by faulthandler patch
in 4.3

- Publish all IO in a thread, via `IOPubThread`. This solves the problem of requiring
`sys.stdout.flush` to be called in
the notebook to produce output promptly during long-running cells.

- Remove references to outdated IPython guiref in kernel banner.

- Patch faulthandler to use `sys.__stderr__` instead of forwarded
`sys.stderr`, which has no fileno when forwarded.

- Deprecate some vestiges of the Big Split:

- `ipykernel.find_connection_file`
is deprecated. Use
`jupyter_client.find_connection_file` instead.

\- Various pieces of code specific to IPython parallel are
deprecated in ipykernel and moved to ipyparallel.

- Don't show interactive debugging info when kernel crashes
- Fix handling of numerical types in json_clean
- Testing fixes for output capturing