I added the tuple unpacking ability.
Example: rule = (-> (1, 2, 3)):(a, b, c)

In order to remove the redudant outer parentheses, I modified the compilePythonExpr inside builder.py.
Now it could support:
rule = (-> 1, 2, 3):(a, b, c)

Also some part related to incremental parsing are modified.
Merge pull request #26 from introom/tuple-unpacking

I added the tuple unpacking ability.