Build cmake branch with AppVeyor.

Former-commit-id: 490ad48bd7c4c2f93417c9a9242dc466d1d1db0c

.appveyor.yml

@@ -6,6 +6,7 @@ branches:
   only:
     - master
     - alecjacobson
+    - cmake
 install:
   - git submodule update --init --recursive
   - cinstall: python