Change Pony ORM version: 0.5.3 -> 0.5.4-dev
Improve the exception message when two entities have more than one relationship and reverse attributes are not specified
Fixes #53: Column generated at the wrong side of one-to-one relationship
Fixes #52: An attribute without a column should not have rbits & wbits
Fixes #51: Handling of one-to-one relations in declarative queries
Typecast object attribute to bool in declarative queries (translates to IS NOT NULL)
Merge branch 'master' to 'orm': bugfixes