- Bump version to 0.3.0
- Update CHANGELOG with 0.3.0 entries
- Remove *.g.dart and *.freezed.dart from .pubignore so pub.dev
  static analysis can resolve generated freezed types
- Shorten pubspec description to pass pub points validation (154 chars)

Signed-off-by: Joel Winarske <joel.winarske@gmail.com>