Require golang 1.9+ (#149)

.travis.yml

@@ -1,10 +1,8 @@
 language: go
 
 go:
-- '1.8'
-- '1.9'
-- '1.10'
-- '1.11'
+- '1.9.x'
+- '1.10.x'
 - '1.11.x'
 - 'master'
 

README.md

@@ -95,6 +95,8 @@ or download the latest Darwin build from the [releases page](https://github.com/
 Download the [latest release](https://github.com/wagoodman/dive/releases/download/v0.6.0/dive_0.6.0_windows_amd64.zip).
 
 **Go tools**
+Requires Go version 1.9 or higher.
+
 ```bash
 go get github.com/wagoodman/dive
 ```