Factorise code in tooltip for julia monkeypatching
Add an Audio display class

This is a first attempt at addressing issue 4241.
Fix unnecerary dependence to numpy
Move imports into methods and fix docstring typo
Fix talk about image embeding in the Audio class.

Too much copy paste I guess :)
Change to encodestring to b64encode to avoid newlines in the data URI

The point of this is to improve compatibility with older browsers.
also, encodestring is depricated in python 3.
Fix extra ) syntax error
Fix broken normalizing when signal array already has integer type

A case of unwanted integer division.
Speed up normalization if numpy is avaliable
Make it explicit that we don't support encoding stereo PCM signals
Remove support for encoding audio without numpy for performance
Partial fix to #3653 (from foo import <tab>)

Some configurability for Julia
(change the regexp because ! is a valid char in token from them)
set_next_input: squash multiple calls from the same cell execution

* When calling multiple times set_next_input in a single cell execution,
  we only keep the last input.

* Added generic support to PayloadManager for updating (instead of
  appending) payloads from a given 'source'.

Closes #1349
Fix style
payload.write_payload: use `single` keyword instead of `update`

* change default behavior when adding payloads to single=True
* document write_payload
remove attic documents from source code
remove unused files
README now includes description of make targets
update help to include html_noapi target
remove do_sphinx file