Update README
Rename README to README.md
Merge master into orm
Fixes #30 issue caused by commit 227727a9 (improved decorators)
Code simplification
Finally fixes #27 collection bug
Set.load bug fixed
Simplification: use None instead of EMPTY for setdata.added and setdata.removed
Fix estore example: use db_session where necessary
Aggregation bug fixed
Merge master into orm: bugfixes