Switching the urls property to use git remote show instead of git remote get-url

`get-url` is a new API that is not widely available yet (introduced in git 2.7.0), and
provokes failure on travis.

Signed-off-by: Guyzmo <guyzmo+github@m0g.net>

Author: guyzmo

git/remote.py

@@ -477,10 +477,10 @@ def delete_url(self, url, **kwargs):
     def urls(self):
         """:return: Iterator yielding all configured URL targets on a remote
         as strings"""
-        scmd = 'get-url'
-        kwargs = {'insert_kwargs_after': scmd}
-        for url in self.repo.git.remote(scmd, self.name, all=True, **kwargs).split('\n'):
-            yield url
+        remote_details = self.repo.git.remote("show", self.name)
+        for line in remote_details.split('\n'):
+            if '  Push  URL:' in line:
+                yield line.split(': ')[-1]
 
     @property
     def refs(self):