Ecru 0.1.3

Time for another Ecru release. This release should be a lot more stable: ctypes is no longer used for the Python interface. The major behaviour change I've added is support for Selfless objects, allowing for value equality: for example, Map objects with the same contents now compare equal. The rest of the work has been in code reorganization and preparation for concurrency support; vats are implemented now, and the REPL executes code by putting it into the vat's event queue. Eventual sends work now (i.e., "foo <- doStuff(x, y)"). Goals for the next couple releases are actual multi-vat execution, support for the 'when' expression, and portability to other OSes.