Fix shlex.split() call to check for posix first

- Currently it assumes posix complience and uses `posix=True`
- This breaks when parsing on windows

pipenv/project.py

@@ -369,8 +369,9 @@ class Project(object):
     @property
     def scripts(self):
         scripts = self.parsed_pipfile.get('scripts', {})
+        posix = os.name == 'posix'
         for (k, v) in scripts.items():
-            scripts[k] = shlex.split(v, posix=True)
+            scripts[k] = shlex.split(v, posix=posix)
         return scripts
 
     def update_settings(self, d):