You can now append a zipfile (containining uncomressed python sources)
to the micropython.hex file.
Use MEMZIP_DIR=directory when you call make, or set that in your
environment to include a different tree of source files.
Added sample /boot.py, /src/main.py, /test.py and /src/test.py files.
Added run command so that you can execute scripts from REPL (until import is implemented).
Added build directory to .gitignore
