Updated Json.net, made polygon serialization

Json.NET was updated to latest version so the lib can be tested with
real world examples
Added test for polygon serialization
Lowered the dependencies
Merge remote-tracking branch 'upstream/master'
Added Polygon deserialization
Merge pull request #6 from gzuri/master

Merging Goran's branch (It keeps getting better and better! Thanks Goran!!)