Add kubectl install

.travis.yml

@@ -1,5 +1,6 @@
 sudo: required
 language: minimal
+dist: trusty
 services:
   - docker
 git:
@@ -18,6 +19,8 @@ before_install:
   - sed -i 's/git@github.com:/https:\/\/github.com\//' .gitmodules
   # Manually initialize submodules
   - git submodule update --init --recursive
+install:
+  - curl -Lo kubectl https://storage.googleapis.com/kubernetes-release/release/v1.10.4/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
 
 before_script:
   - rm -rf ./crl/*