Added JsonSerializable interface, based on the PHP.net documentation
Added stubs directory to composer.json, so the autoloading mechanism of Composer can be used.
Implemented JsonSerializable in Table, as suggested in issue #2.
Merge branch 'master' into dev-stubs
Added unit test to verify stub and implementation of JsonSerializable in Table
Merge pull request #6 from itavero/dev-stubs

Support for JsonSerializable. Fixes #2