fix travis.yaml

Author: yuin

.travis.yml

@@ -3,7 +3,7 @@ language: go
 go:
   - "1.8"
   - "1.9"
-- "1.10"
+  - "1.10"
 
 before_install:
   - go get github.com/axw/gocov/gocov
@@ -12,4 +12,4 @@ before_install:
 install:
   - go get -u -v $(go list -f '{{join .Imports "\n"}}{{"\n"}}{{join .TestImports "\n"}}' ./... | sort | uniq | grep -v gopher-lua)
 script:
-    - $HOME/gopath/bin/goveralls -service=travis-ci -vetoff
+  - $HOME/gopath/bin/goveralls -service=travis-ci -vetoff