Add support to embed videos.
Raise better IOError if a connection file is not found

when starting parallel.Client

Example:

    IOError: Connection file u’~/.ipython/profile_default/security/ipcontroller-client.json' not found. Is a controller running?
Add is_complete request and reply to messaging infrastructure
Expose IPython machinery for testing code completeness
Document is_complete messages

Also, bump message spec version
Use the more powerful signatures module to display function argument signatures. In particular this works better for functions wrapped with functools.wraps (at least on Python >= 3.4)
Four possible states for completion reply, & indent hint
Set protocol version number back to 5.0

Bumping to 5.1 wasn't necessary, because we're still finalising 5.0
(thanks @minrk)
add new FilesHandler to serve files from ContentsManager.
add new FilesHandler class
Allow widget views to be loaded from require modules

This required refactoring things that create widget views to use
callbacks instead of return values.
Make changes suggested by @jdfreder
Fix logic
Put callbacks for create_view and create_child_view in options

And add errback support
Clean up some JS code
add tests for file download via ContentsManager
mark binary properly as binary for python 3
get bin test file to pass. (2nd try)
3rd
add tests for file download via ContentsManager