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
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)
Fix bug in bounded int/float logic.
remove cython extension.

Now in cython package itself, as stable.
remove Cython Built-in extension notebook
remove more ref to cythonmagic
use Cython.load_ipython_ext to simplify
add whatsnew and uppercase C in load_ext

Use uppercase as this is what is in cython docs.
Added test
Use contentEditable to allow modification via the the slider readout
Add support to the float slider
Add keydown listener to commit changes on <enter>
Ignore the event object for handleTextChange
Add support for parsing pairs of numbers for range sliders
Change _parse_text_input to _parse_value and update float range regex