Merge shlex PRs (#1130,
#1116)
* arg_split now takes optional strict flag, to ignore ValueErrors in
shlex parsing
* %timeit uses strict=False, to avoid errors parsing python code
* %run completer uses arg_split(strict=False) for its unicode behavior, instead
of custom shlex derivative, which is now redundant.
closes
#1109
closes
#1115
closes
#1116
closes
#1130
