Temporarily only test docker

.travis.yml

 language: rust
 sudo: required
-rust:
-  - 1.0.0
-  - beta
-  - stable
+# rust:
+#   - 1.0.0
+#   - beta
+#   - stable
 services:
   - docker
 script:
   - sh ci/run-travis.sh
-os:
-  - linux
-  - osx
-env:
-  - ARCH=i686
-  - ARCH=x86_64
+# os:
+#   - linux
+#   - osx
+# env:
+#   - ARCH=i686
+#   - ARCH=x86_64
 matrix:
   include:
     - os: linux