Add Pony ORM documentation
Update README.md
Merge master into orm: documentation added
Add OptimisticCheckError(IsolationError) exception and use it when the optimistic check fails on saving updated object
Merge master into orm: OptimisticCheckError instead of UnrepeatableReadError
Remove unused code
Optimization: using obj._pk_attrs_ or obj._pk_attrs_[0] instead of obj.__class__.__dict__['_pk_'] if possible
Optimization: using defaultdict(dict) instead of dict for cache.indexes
Optimization: using defaultdict(set) instead of dict for cache.seeds
Optimization: entity._subclasses_ implies entity._discriminator_ is not None
Renaming: _keys_ -> _key_dict_
Minor rbit bug fixed
Minor optimization & test coverage
Minor change & test coverage
Minor code simplification
Now all attributes which previously were missed from entity._bits_ (pk and collection attributes) are presented here, and have zero mask instead of a specific bit
Inheritance-related bug fixed in EntityMeta._find_
Inheritance-related bug was fixed; EntityMeta._set_rbits(objects, attrs) method was extracted
Merge master into orm: optimizations & bugfixes
Now INSERT command does not save NULL values explicitly