Dispose isolate when freeing V8Js object.
Exit current isolate on fatal V8 error.
Also perform isolate exit on fatal error abort.
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.
Merge pull request #102 from stesie/dispose-isolate

Dispose isolate on V8Js object destruction