only test against 1.8

.travis.yml

@@ -2,7 +2,6 @@ language: go
 
 go:
   - 1.8.x
-  - tip
 
 before_install:
   - go get -t -v ./...
@@ -11,4 +10,4 @@ script:
   - ./test.sh
 
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)