Merge branch 'Gopkg-fix' into 'master'

Update Gopkg.toml

See merge request !60

Gopkg.toml

@@ -14,6 +14,10 @@
   name = "google.golang.org/grpc"
   version = "1.13.0"
 
+[[constraint]]
+  version = "=v1.6.3"
+  name = "github.com/spf13/viper"
+
 [prune]
   go-tests = true
   unused-packages = true