Add textInput binding.
Include the ability to test certain textInput functionality through internal APIs available in the DEBUG version.
Improve textInput comments
fix browser version detection; catch dragdrop event in early Firefox versions.
Make sure "mobile safari" doesn't match "safari"; catch additional events in early Firefox versions.
Testing in early Safari showed that textInput isn't good enough for textarea elements. Switch to using keydown, cut, and paste events.
Use propertychange in IE9 also to catch autocomplete.
Merge pull request #1160 from knockout/1160-input-binding

Add 'input' binding for real-time updates from text fields