Update to the ServiceStack version dependency

Since SS v4 is a major change including licensing and commercial use, this limits the dependencies to the v3 releases.
Merge pull request #5 from parnham/patch-1

Update to the ServiceStack version dependency
Updated submodule to tag: v0.22.0
Updated submodule to tag: v0.22.1
Updated submodule to tag: v0.22.2
Prevent TargetException when getting property value
Merge pull request #7 from khellang/patch-1

Prevent TargetException when getting property value
Updated submodule to tag: v0.23.0
Updated submodule to tag: v0.23.1
Updated submodule to tag: v0.23.2