Make testify a testImport for consistency

glide.yaml

@@ -11,9 +11,6 @@ import:
 - package: github.com/pkg/errors
 - package: github.com/spf13/cobra
 - package: github.com/spf13/viper
-- package: github.com/stretchr/testify
-  subpackages:
-  - require
 - package: github.com/tendermint/abci
   version: develop
   subpackages:
@@ -49,6 +46,11 @@ import:
   - context
 - package: google.golang.org/grpc
 testImport:
+- package: github.com/stretchr/testify
+  version: ^1.1.4
+  subpackages:
+  - assert
+  - require
 - package: github.com/tendermint/merkleeyes
   version: develop
   subpackages: