store default codemirror mode in only 1 place
do not include specific css in embedable one
catch if cm_config of other key undefined
cleanup Client.close

allows setting `linger` on sockets at shutdown time.
close Client sockets if connection fails

avoids runaway FDs in cases of frequent client failure.
Implement a better check for hidden values for %who etc.
Tweaks to interactiveshell for user_ns_hidden as dict
FIX: nbconvert unicode html header characters (Win + Py2.x)
Reference notebook examples, fixes #4146.
generate choices for `--gui` configurable from real mapping

typo prevented `--gui tk` from working, even though it is supported.
Should prevent similar bugs in the future.

closes #4156

should be backported to 1.1
Merge pull request #4064 from Carreau/default_mode

Store default codemirror mode in only 1 place
Merge pull request #4074 from minrk/close-on-fail

close Client sockets if connection fails

also cleanup Client.close a little bit, allowing setting linger on sockets at shutdown time,
which is helpful for preventing FD growth on connection failure.

Should be considered for backport to 1.1.
Merge pull request #4092 from jdfreder/japanese

nbconvert: Fix for unicode html headers

Closes #3818
Merge pull request #4065 from Carreau/ecss

do not include page css in ipython.min.css
Merge pull request #4147 from kermit666/patch-1

Reference notebook examples in docs.
Merge pull request #4083 from takluyver/better-hidden-ns

Implement a better check for hidden values for %who etc.
clean up imports
fix bug in mathjax

previously, if from IPython.external.mathjax import * was called, it
would cause an error, since the dest variable was renamed to
default_dest
Merge pull request #4158 from minrk/guitk

generate choices for `--gui` configurable from real mapping

typo prevented --gui tk from working, even though it is supported.
Should prevent similar bugs in the future.

closes #4156
Merge pull request #6 from ivanov/parametric-begone

remove unused imports