Support Hibernate 4 in addition to Hibernate 3. Fix bug #193.
Merge pull request #34 from cyrille-leclerc/fix-bug-193

HibernateCollectionsSerializerFactory: Support Hibernate 4 in addition to Hibernate 3. Fix bug #193.
Add samples that can be run with tomcat maven plugin
Fix #137: "Found no validity info for session" warnings after invalidating session
Improve logging regarding ping results
Fix typo, add README to simpleservlet sample