Fix IPython.utils.path when HOME=/.
Fix subrepos.
Pop out any existing IPYTHONDIR or IPYTHON_DIR variables.
s/os.path.split/os.path.dirname/
remove long-dead zmq frontend.py and completer.py

These were really just demos to begin with, and should never have been included as library code.

closes #3365
Use different threshold for (auto)scroll in output

Allow, in particular to switch to scolling for longer input (or disable
it) by still keeping the possibility to manually toggle the output to
scroll.
improve js documentation
rename scroll_threshold, add minimum_ prefix
document undefined behavior for 0 parameter
set autoscroll default back to 100
Update gitwash_dumper.py

comments updated
Merge pull request #3384 from ugurthemaster/master

comments in tools/gitwash_dumper.py changed (''' to """)
Merge pull request #3319 from minrk/user-expressions

IPEP 13: user-expressions and user-variables

The user-expressions and user-variables side effects in execute_requests are updated to use the rich-repr display data identical to a display_data message.

closes #2654
Merge pull request #3330 from AnIrishDuck/master

Fix get_ipython_dir when $HOME is /
Merge pull request #3382 from minrk/culldigest

cull Session digest history

a randomly selected ten percent is culled from the history

prevents infinite growth for long running sessions of many messages, while maintaining reasonable replay protection.

Size of digest is Configurable.
related to #1131
Merge pull request #3366 from minrk/rmfrontend

remove long-dead zmq frontend.py and completer.py

These were really just demos to begin with, and should never have been
included as library code.

closes #3365
Merge pull request #3371 from minrk/dirty-event

make setting the notebook dirty flag an event
Merge pull request #3358 from minrk/cm-scroll

workaround spurious CodeMirror scrollbars
Merge pull request #3378 from minrk/dragDropSafari

disable CodeMirror drag/drop on Safari
Merge pull request #3372 from minrk/cookiename

base default cookie name on request host+port