Update dependencies.
Trying to support buster-assertions
Do not depend on existence of 'ok' method when empowering a function.
Reorganize tests.
Test buster-assertions support on browser.
Test buster-assertions support on browser with RequireJS.
Add documentation about supported assertion libraries.

Add 'SUPPORTED ASSERTION LIBRARIES' and 'ASSERTION LIBRARIES KNOWN TO WORK' section.
Merge pull request #5 from twada/buster

Support buster-assertions