Wrap getComputedStyle

Fixes #64
Implement event constructors for Safari and IE

This implements event constructors for

Event
CustomEvent
UIEvent
MouseEvent
FocusEvent

More can easily be added as needed.

Fixes #58
Update README.md
Merge branch 'master' of github.com:toolkitchen/ShadowDOM
Merge branch 'master' of github.com:arv/ShadowDOM