Use fast-submodule-update in CI

Hopefully this will speed up CI builds.

.travis.yml

@@ -4,6 +4,7 @@ before_install:
   - git fetch origin test/attributes:test/attributes
   - git fetch origin test/master:test/master
   - sudo apt-get install libicu-dev -y
+  - script/fast-submodule-update
 rvm:
   - 1.9.3
   - 2.0.0
@@ -11,3 +12,5 @@ rvm:
   - 2.2
 notifications:
   disabled: true
+git:
+  submodules: false