use `pip install .[all]` on travis

can't actually use `.[all]` syntax, instead using `file://$PWD`,
but the principal is the same.

get wheels from minrk/travis-wheels to expedite installation
remove timings in travis.yml

Travis does its own timing now
add 'requests' as test dependency

since it is one
upate exmaple notebooks to nbformat v4
DEV: Support for configurable list of extra jinja template directories.
DEV: Add IPython.html to the default template path.

This makes it possible to override a file with a template that also
inherits from that file.

For example, this makes it possible to override a single block of
notebook.html by creating a file called notebook.html that inherits from
templates/notebook.html.
DOC: Fix typo in comment.
Merge pull request #6835 from minrk/travis-pip

expedite installation on travis
JS Contents API doesn't need dialog module
Merge pull request #6873 from takluyver/contents-api-no-dialog

JS Contents API doesn't need dialog module
DOC: Add whatsnew entry for userspace templates.
Merge pull request #6861 from quantopian/template_dir_option

DEV: Support for configurable list of extra jinja template directories.
Fix typo in docstring.
Merge pull request #6880 from francisco-dlp/fix_typo

Fix typo in docstring.
Document limitations of symlink parameter to install_nbextension

Closes gh-6239
Merge pull request #6882 from takluyver/i6239-docstring

Document limitations of symlink parameter to install_nbextension
Merge pull request #6843 from minrk/nbformat4-examples

update example notebooks to v4
DEV: Forward this_class in container traits.

Makes it possible to do things like List(This()) and have This()
correctly refer to the parent class.
DEV: Add ForwardDeclaredType and ForwardDeclaredInstance trait types.

These traits take advantage of the this_class attribute to resolve a
supplied name relative to the module in which the containing class was
defined.  You can hack this already by leveraging `__name__`, but this
implementation makes it a bit clearer what you're actually trying to do.