Limit latex equations to page width.
Fixed latex template to support multicol w/ adjustbox.
send idle/busy on all shell messages

Instead of just those that execute code.
This means that kernel_info_request triggers busy/idle,
allowing clients to check IOPub channel status without executing code.
Set axis background to transparent in inlinebackend

Fixes #5727, related to #4608
set busy/idle around every message

not just shell
Updated license to include CC BY 4.0 for documentation, examples, and other materials
Added examples to BSD, and added links to online versions of CC-BY
Moved the list of links of the CC-BY licenses below (I could not get RST to render correctly)
Update bundled copy of pexpect to 3.3

Closes gh-6086
i1673 PEP8 formatting in `ultratab.py`
i1673 implementation of py3 proper error handling

I refactored ultratab.py a bit. `structured_traceback`
function was much too long. I extracted some of the code
to separate methods.

I added support for py3
exceptions which store information about previous
exceptions in their `__context__`.
i1673 some DRY refactoring
i1673 don't use __suppress_context__ attribute
i1673 fix py2 bug in ultratb
i1673 add tests for python3 exceptions
i1673 remove confusing traceback truncating
i1673 change formatting (dashed line only on top)
i1673 use __cause__ first in chained exceptions
i1673 rerun notebook with exceptions in nbconvert
fix Session inheritance for frontends with `--existing`

The Client was getting a new Session without the connection info loaded from the file,
which would cause `Invalid Signature` errors to be logged,
and no prompt to appear in the frontend.