add enable() and disable() methods
fix package links
fix when pointer.identifier might be 0

As it was when testing Opera Mobile Emulator

Ref #4
tick version in js
add enable() and disable() methods
Merge branch 'master' into site
draggies get z-index; Fixes #9
move instance to version argument;
require get-size v1;
fix event names for the contained draggies
Merge branch 'master' into site
Merge branch 'site' of github.com:desandro/draggabilly into site