Choose required kerberos package depending on platform

.travis.yml

@@ -3,4 +3,6 @@ python:
     - "2.6"
     - "2.7"
 
+install:
+    - pip install .
 script: py.test test_requests_kerberos.py

requirements.txt

@@ -1,2 +1 @@
 requests>=1.1.0
-kerberos==1.1.1

setup.py

@@ -1,12 +1,18 @@
 #!/usr/bin/env python
 # coding: utf-8
 import os
+import sys
 import re
 from setuptools import setup
 
 with open('requirements.txt') as requirements:
     requires = [line.strip() for line in requirements if line.strip()]
 
+if sys.platform == 'win32':
+    requires.append('kerberos-sspi')
+else:
+    requires.append('kerberos==1.1.1')
+
 path = os.path.dirname(__file__)
 desc_fd = os.path.join(path, 'README.rst')
 hist_fd = os.path.join(path, 'HISTORY.rst')