Clean up task interface and add testing. (#34)

* Update c extensions and python tests.

* Updates.

* Documentation fix.

* Move c extensions into common_extension.c

lib/python/setup.py

@@ -1,7 +1,7 @@
 from setuptools import setup, find_packages, Extension
 
 common_module = Extension("common",
-                          sources=["object_id.c", "serialization.c", "task.c"],
+                          sources=["common_extension.c"],
                           include_dirs=["../../", "../../thirdparty"],
                           extra_objects=["../../build/libcommon.a"],
                           extra_compile_args=["--std=c99", "-Werror"])