Add initial unit tests

[drofp]

We should have test coverage for some of the critical functions that are easy to test.

This will probably require the following steps

• Decouple non-ncurses logic from ncurses calls into separate functions. It may help to create our own convenience library to call common ncurses patterns (like mvwprintw() followed by wrefresh()) or just mocking out some of the ncurses calls.
  • Ron Mak would be proud of our interface segregation here
• Actually write the tests for non-ncurses functions.

Other intersting things:

• CUnit might be useful