Don't explicitly depend on XModule--bootstrapping dependencies in the platform…

Don't explicitly depend on XModule--bootstrapping dependencies in the platform build in the right order seems to be tricky.

setup.py

@@ -5,6 +5,5 @@ setup(
     version="1.0",
     packages=find_packages(exclude=["tests"]),
     install_requires=[
-        'XModule',
     ],
 )