Added `toxPreGet()' and `toxPostSet()' hooks on retrieving and setting magic properties.
Reorganized interfaces of models and sets.
Added the unit-test for models entities.
Resolved a sequence issue on pre and post setting properties of assemblies.
Rewritten the models entities.
Moved the definition files of exceptions to follow `PSR-0'.
Updated the model entities to keep created ones in memory.
Added the unit-test for models sets.
Rewritten the models sets. (Edit features not implemented.)
Supported sync mode in model entities.
Supported importing for Sets in Model entities.
Improved the model entity for operating committable properties immediately.
Implemented modification features for models sets.
Supported sync mode in model sets.
Merged php-tox/tox.
Merge pull request #84 from snakevil/master

Fixed #33.