[fix] moved callback outside try block, which prevents callback being called twice when there is throw inside callback. [test] a few small changes to simplify testing. [doc] update some comments.
[fix] moved callback outside try block, which prevents callback being called twice when there is throw inside callback.
[test] a few small changes to simplify testing.
[doc] update some comments.

rowhit/jitsu,mbejda/jitsu,nodejitsu/jitsu