removes unnecessary lib/chess mapping from require config in test runner
removes redundant colour parameter from Position.countLegalMoves

only the active colour can legally move...
adds Position.getLegalMoves

returns {from, to} objects for all the current legal moves, in an array
updates repo url in package.json
updates require paths
moves requirejs from dependencies to devDependencies

modules use the requirejs format, but the requirejs library is only
actually called from runtests.  To use the library, the calling code
will need to have requirejs anyway.