Allows handlers without arguments, and ignores void returns
Merge branch 'relaxed' of https://github.com/darscan/promise-as3 into darscan-relaxed
Fixed a bug in nextTick() where the optional parameters argument was ignored when specified.
Integrated "allow handlers without arguments" pull request.

Applied changes discussed in pull request comments.
Rolled back changes to support undefined returns - prefer to maintain Promises/A+ specification compliance.
Per Shaun's suggestion, changed Resolver internal methods from protected to private.

Fixes #13