Make compatible with V8 3.28.23, fixes #99
IdleNotification is on Isolate now
GetConstructor method was removed, use GetConstructorName and instanciate on our own
Add test on constructor get-accessor.
Don't explicitly indicate constructor, let V8 figure out

The GetConstructor function was removed from v8::Object which
would require some work to find out.  But V8 can do it
internally, so just leave it to V8 :)
zend_fetch_class_by_name is not available in PHP 5.3
Merge remote-tracking branch 'rosmo/dispose-isolate'
Keep a list of disposed isolates and make sure not to use disposed isolates.
Keep track of V8Object/V8Function instances

Disallow access to these once the V8Js object has been destroyed.