Fixed Embed.
(Id was not mapped, and createdOn could not be parsed).
Added serialization to some classes.
Further support for Serialization - now Item should be completely
serializable.
Merge branch 'master' of https://github.com/podio/podio-java
removed ./settings/org.eclipse.m2e.core.prefs
Removed custom Json deserializer and added Java Serializable support.
Merge pull request #7 from daniel-sc/master

Fixed Embed.