Remove dependency of System.Runtime.Serialization.dll

Remove the references for DataContractAttribute and DataMemberAttribute
and re-implement with reflection-based attribute retrieving.
Fix typo.
Fix abstract dictionary types in winRT causes Exception.
Fix build issues related to PR #29.
Add test for merging PR #30
Fix changelog.
Merge remote-tracking branch 'origin/0.4' into 0.4
Unity projects.