Deactivate tooltip on tab by default.

Codepath is **not** removed by this.
Update some example notebook with Shift-Tab
Remove tooltip on tab logic
make close-and-halt work on new tabs in Chrome

this is not possible in Firefox, as new tabs/windows which were *not*
opened via a script ( window.open call ) are not allowed to be closed
via window.close and will yield a message like

--
[11:50:59.691] Scripts may not close windows that were not opened by script. @ http://localhost:8888/static/notebook/js/menubar.js:105
Bundled path.py should not modify the os module
Python 3 compatibility for os.getcwdu()
test that config objects are pickleable
don't create LazyConfigValue on `__` config names

closes #4447
cleanup Config attributes

fixes pickling on Python 3

- don't override get/setattr on dunder names
- fix branching bug in __setitem__
- remove setting `__dict__` attribute
- make _is_section_key a function, not a method
update builtin test - we don't exec in config objects
Merge pull request #4469 from takluyver/py3-getcwdu

Python 3 & getcwdu

We were using the os.getcwdu() function in several places. That doesn't exist on Python 3, but the path.py module was masking that by setting os.getcwdu = os.getcwd. As described in #4462, however, that didn't always work.

This adds a reference in py3compat which points to getcwd on Python 3 and getcwdu in Python 2.
Merge pull request #4410 from ivanov/close-new-tabs-chrome

make close-and-halt work on new tabs in Chrome
Allow incremental builds of the html_noapi docs target
Fix up some problems with parallel docs
Don't document classes defined in if __name__ == '__main__' blocks
Another fix to parallel docs
yet another JS race condition fix

this should greatly reduce the number of timeouts seen in the JS tests
Remove dead links from whatsnew 0.11 doc
Miscellaneous doc fixes
Fix doc reference