Run make verify-version during Travis build

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 0078c9c..8b4daa9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,7 +18,7 @@
 # in the vendor directory. We don't need to test all dependent packages.
 # Only testing this project.
 script:
-  - GO15VENDOREXPERIMENT=1 make test integration-test
+  - GO15VENDOREXPERIMENT=1 make test integration-test verify-version
 
 notifications:
   webhooks: