Add python 3.7 support.

.travis.yml

@@ -8,7 +8,7 @@ python:
   - 3.4
   - 3.5
   - 3.6
-  - 3.6-dev
+  - 3.7
   - pypy3.5
 
 env:

README.rst

@@ -93,4 +93,5 @@ file and `list of open issues <https://github.com/dulwich/dulwich/issues>`_.
 Supported versions of Python
 ----------------------------
 
-At the moment, Dulwich supports (and is tested on) CPython 2.7, 3.4, 3.5, 3.6 and Pypy.
+At the moment, Dulwich supports (and is tested on) CPython 2.7, 3.4, 3.5, 3.6,
+3.7 and Pypy.