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.
FIX: nbconvert unicode html header characters (Win + Py2.x)
Add way to install MathJax to a particular profile
Make profile not set a default
Made profile the default install option, install_dir the explicit
simplify join
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
don't split `.cell` and `div.cell` CSS

`.cell` matches non-IPython things that it shouldn't (inside highlighted code),
everything `.cell` should match in IPython is a div.
fab css
Quote notebook install

ZSH needs the quotes to treat the argument properly
Select default title when renaming a notebook

The default notebook name is Untitled<x>. It is unlikely the user will want to
keep this name or part of it. Instead, select the text in the input field so the
user can easily type over the name and change it.
Add feature description to whatsnew
Merge pull request #4144 from takluyver/i4134

help_end transformer shouldn't pick up ? in multiline string

The help_end() transformer was already tokenizing the line to determine whether the ? was in a comment, so I just extended this to check for multi-line strings as well.

Closes #4134
Merge pull request #4160 from kevinburke/quote-readme

Add quotes around ".[notebook]" in readme
Merge pull request #4161 from kevinburke/select

Select name when renaming a notebook