Include pyx/pxd files in source distributions.

Author: Pan

.travis.yml

@@ -25,6 +25,8 @@ install:
 script:
   - nosetests
   - flake8 ssh2
+  - python setup.py sdist
+  - cd dist; pip install *; cd ..
 jobs:
   include:
     - stage: OSX wheel build

MANIFEST.in

@@ -3,3 +3,5 @@ include versioneer.py
 include ssh2/_version.py
 exclude .travis.yml
 include LICENSE
+include ssh2/*.pyx
+include ssh2/*.pxd