renamed piece_test to pawn_test
moved valid_move and valid_attack to Piece class
added in_bounds property to position
added directional iterators to position
removed __contains__ and __iter__ from board in favor of explicit squares() and positions() iterators
Standardized on uppercase notations
added positions iterator to board
added tests for board

moved a test from pawn_test.py to board_test.py
moved str, repr, and notation to Piece
made __repr__ for Color return the fully qualified name
added rook piece type and rook tests
added simple implementation of bishop, queen, king, and knight piece types
added simple move controller
added client module with helper functions for interacting from console
added starting notation constant for a starting board
added tkinter gui client
added icons for pieces and movable squares