Handle a path of / in Repository.get_contents() (#1070)

The path requested in Repository.get_contents() is appended to the URL,
so the root path should be requested with the empty string. If path is
'/', set it to the empty string. Copy the replay data from the original
test, since it is identical.

Drive-by renaming the test to include the missing 's'.

Closes #1059

github/Repository.py

@@ -1478,6 +1478,9 @@ class Repository(github.GithubObject.CompletableGithubObject):
         """
         assert isinstance(path, (str, unicode)), path
         assert ref is github.GithubObject.NotSet or isinstance(ref, (str, unicode)), ref
+        # Path of '/' should be the empty string.
+        if path == '/':
+            path = ''
         url_parameters = dict()
         if ref is not github.GithubObject.NotSet:
             url_parameters["ref"] = ref