v.2.2

This releases primarily changes the when() method, adding the following improvements:

• when() now supports calling it with no arguments
• .promise() can be called on promises
• $.when() can handle non-deferred arguments, and treats them as pre-resolved deferreds. This turns out making $.when(...) with all resolved arguments a shorthand for $.Deferred().resolve(...).promise(). jQuery treats every object that implements a .promise() function as a deferred. This has special implications for .pipe().

Most of the work for this release was done by @rraval via #14 - so a big thank you goes there.

Bumping to 2.2 because this may break code that relies on these features not being present.