Accept some golint suggestions (#690)

* Fixed some linter issues

* Simplified isBetter method

* Accept some linter suggestions

* Fix typo

Co-authored-by: klesomik <klesomiks@gmail.com>
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

src/crypto/crypto.go

@@ -272,7 +272,7 @@ func (n *BoxNonce) Increment() {
 	n[len(n)-1] += 2
 	for i := len(n) - 2; i >= 0; i-- {
 		if n[i+1] < oldNonce[i+1] {
-			n[i] += 1
+			n[i]++
 		}
 	}
 }