v0.1.3a

New features:

- Multiplayer added;
- Login option;
- Connection to server required;
- Black piece's full movement (including pawns);
- Turn alternation;

Improvements:

- New code organization;

Known issues:

- No check and checkmate recognition (game only ends when someone
disconnects);
- No account creation (must be done manually);
- Missing some situations checking in the login screen;