Fix for MongoDB 1.8.1.

Triggers were not getting serialized correctly. This seems to fix the problem
https://github.com/chrisdrobison/quartznet-mongodb/commit/c996028f05a1ff786721d40dbae18dc5e0b7997a#diff-0
Merge pull request #13 from andrevdm/master

Fix for MongoDB 1.8.1 trigger serilization