Increase compatbile versions with simple-ddl-parser and omymodels

[hyamanieu]

FYI, I have just used your library to produce an SQLalchemy model from a DBML file.
It actually did not work due to too old versions of simple-ddl-parser and omymodels. Using the latest versions simple_ddl_parser-0.31.0 and omymodels 0.14.0 did work.

I know that the dependency model of omymodels limits simple_ddl_parser to 0.28.1, but well, it still worked making 98% of the job for me. Great job! Thanks.

I simply ran your CLI command.

My schema was "fairly" complex with enum, various foreign key relationships, and various data types.