Fix #11: actually install all files.

Especially, installs `__init__.py` which is necessary for the import.

README.md

@@ -41,7 +41,7 @@ For images, the easiest way to use this library is using the `DenseCRF2D` class:
 
 ```python
 import numpy as np
-import densecrf as dcrf
+import pydensecrf.densecrf as dcrf
 
 d = dcrf.DenseCRF2D(640, 480, 5)  # width, height, nlabels
 ```

setup.py

@@ -14,6 +14,6 @@ setup(
     author_email="lucasb.eyer.be@gmail.com",
     url="http://github.com/lucasb-eyer/pydensecrf",
     ext_modules=cythonize(['pydensecrf/eigen.pyx', 'pydensecrf/densecrf.pyx']),
-    py_modules = ["pydensecrf/utils"]
+    packages=["pydensecrf"]
 )