Fewer string constants used in minification for smaller final size

tested via closure compiler -- removing STR_ON and adding "on" to the strings it was being concatenated to reduces the overall file size slightly.

(As a side effect, the code is simpler to read)
Support for loading as an AMD module

Allow the plugin to be loaded as an AMD module.  For more details, see:
http://requirejs.org/docs/whyamd.html

As a side effect, this prevents things from being instantiated multiple times if the script is included more than once on the page.
Update jquery.jsonp.js
Update jquery.jsonp.js

Also fire complete callback on abort to give similar behavior to jQuery's $.ajax complete / always
Update API.md
Defines as an AMD module when available
Returns the jsonp function as the AMD module
remove STR_ON

I think it will save 4 bytes after minification, and it's more readable.
Merge remote-tracking branch 'remotes/timtucker/patch-1'

Conflicts:
	src/jquery.jsonp.js
Merge remote-tracking branch 'remotes/timtucker/patch-3'
Merge remote-tracking branch 'remotes/hull/feature/amd'
Merge remote-tracking branch 'remotes/timtucker/patch-2'

Conflicts:
	src/jquery.jsonp.js
use local copy of qunit; git submodule is fine, but tests should run out of the box.
ignore editor bak files