Make `--unicode`behaviour the standard

[ClasherKasten]

Right now the CLI provides an option named --unicode or -u which uses unicode characters to display the pieces. If the option isn't used, then it falls back to "normal", non-unicode characters. In the process of switching out termcolor to colored We noticed that it is really hard to display a colored board with non-unicode characters.

To fix this, I decided to remove the non-unicode character support and make the --unicode behaviour standard. ToDo:

• remove --unicode option as it is the default
• remove all the code that don't need to exist anymore (E.g. the makeStringRep method)

[aitorres]

Hi! I opened a PR (#43) for this issue, let me know if there's anything else I should add to it!