alias amino imports (#3219)

As per conversation here: https://github.com/tendermint/tendermint/pull/3218#discussion_r251364041

This is the result of running the following code on the repo:

```bash
find . -name '*.go' | grep -v 'vendor/' | xargs -n 1 goimports -w
```

consensus/wal_test.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+
 	// "sync"
 	"testing"
 	"time"