Fixed null optional strings serialized to "null"
Merge pull request #32 from elaberge/master

Fixed null optional strings serialized to "null"
Fixed undefined optional strings serialized to "undefined"
Merge pull request #34 from elaberge/master

Fixed undefined optional strings serialized to "undefined"
Released v1.1.1
Merge branch 'master' of github.com:fuwaneko/node-protobuf