Add submenu under kernel for changing kernel
Merge pull request #6139 from minrk/wsping

send ping every 30 seconds to keep websockets alive
add marked to require dependencies
Merge pull request #6208 from bavardage/master

add marked to require dependencies
fix missing semicolons
Address review comments
Don't screenshot in the ImageWidget test,
instead verify that the base64 makes it to the page and
assume that the browser knows how render it correctly.
Merge pull request #6204 from minrk/xs-cluster-columns

move some responsive bootstrap transitions
Merge pull request #6182 from SylvainCorlay/do-diff-correction

do_diff function was always removing all views from the old list.
Put missing doc in TOC
Exclude kernel.zmq.gui package from docs
Mark mistune machinery as not part of public API for docs
Add whatsnew entry for selecting kernels
Merge pull request #6210 from jdfreder/image-test-fix

Don't screenshot in the ImageWidget test,
Merge pull request #5694 from jgoppert/latex-eq-fit

Limit latex equations to page width for nbconvert.
Merge pull request #6063 from Carreau/fix-5984

Introduce info/warning/danger to notification area
deleting a comm now unregisters the comm. unrehistering the comm does not close it anymore
add gtk3 support to ipython kernel
decoupling the comm lifetime from the widget lifetime
exclude gtk3 gui modules from tests