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
distinguish capture_output from buffer_output

allow capturing output without silencing it,
which is useful for slimerjs,
which requires looking at output to determine failure.
DEV: Support for configurable list of extra jinja template directories.
Merge pull request #6860 from minrk/slimerjs

distinguish capture_output from buffer_output
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.
Update components to codemirror 4.7
Merge pull request #6865 from takluyver/cm4.7

Update components to codemirror 4.7
allow multiple forms of latex math in test_markdown

different versions of pandoc use different escapes
Merge pull request #6863 from minrk/markdown-tex-math

allow multiple forms of latex math in test_markdown
upgrading >v4 header cells to unicode

adding test
more human-readable unicode chars in test
Merge pull request #6868 from bollwyvl/unicode-upgrade-headers

upgrading >v4 header cells to unicode
fix unicode literal in v4.test_convert

caused failure on Python 2 on Windows

because unicode!
Merge pull request #6870 from minrk/unicode-literal-fix

fix unicode literal in v4.test_convert
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