Added a load function to the capnp module

It takes .capnp file and will load it through the C++ capnproto library.
Only major thing left is initializing lists and structs in
MessageBuilder

setup.py

@@ -3,5 +3,5 @@ from distutils.core import setup
 from Cython.Build import cythonize
 setup(
     name = "capnp",
-    ext_modules = cythonize('capnp.pyx'),
-)
+    ext_modules = cythonize('*.pyx'),
+)