Include missing pyx files in dist file.

Closes #168

CHANGES

@@ -8,6 +8,7 @@ Version 0.15
 
 (feature release, released on X)
 - Fix Python 3.2 compatibility issue with noatime open() (#164)
+- Include missing pyx files in dist files (#168)
 
 Version 0.14
 ------------

MANIFEST.in

@@ -1,4 +1,5 @@
 include README.rst LICENSE CHANGES MANIFEST.in versioneer.py
+recursive-include attic *.pyx
 recursive-include docs *
 recursive-exclude docs *.pyc
 recursive-exclude docs *.pyo