chore: upgrade travis config format

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.travis.yml

@@ -1,20 +1,16 @@
 language: go
-sudo: false
 
-go:
+jobs:
-  - 1.11.x
-  - 1.12.x
-  - 1.13.x
-  - 1.15.x
-  - master
-
-matrix:
   fast_finish: true
   include:
   - go: 1.11.x
     env: GO111MODULE=on
   - go: 1.12.x
     env: GO111MODULE=on
+  - go: 1.13.x
+  - go: 1.14.x
+  - go: 1.15.x
+  - go: master
 
 install:
   - go get -t -v -d
@@ -33,4 +29,4 @@ notifications:
       - https://webhooks.gitter.im/e/acc2c57482e94b44f557
     on_success: change
     on_failure: always
-    on_start: false
+    on_start: never