Use mod vendor for vendored directory (backwards compatible)

vendor/github.com/labstack/echo/.travis.yml

@@ -0,0 +1,14 @@
+language: go
+go:
+  - 1.8.x
+  - 1.9.x
+  - tip
+install:
+  - make dependency
+script:
+  - make test
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
+matrix:
+  allow_failures:
+    - go: tip