Fix CLI test after changing error message in previous commit.

Add Makefile.
Update travis yaml.

Author: andystanton

.travis.yml

@@ -1,3 +1,6 @@
 sudo: false
 language: go
-script: go test . ./cli ./dexec ./util
+go:
+  - "1.12.x"
+env:
+  - GO111MODULE=on

Makefile

@@ -0,0 +1,6 @@
+.PHONY : all test
+
+all: | test
+
+test:
+	@go test

cli_test.go

@@ -23,8 +23,8 @@ func TestUnknown(t *testing.T) {
 		want WantedData
 	}{
 		{
-			OptionData{"-bad", "Unknown option: -bad"},
-			WantedData{None, "", 0, "Unknown option: -bad"},
+			OptionData{"-bad", "unknown option: -bad"},
+			WantedData{None, "", 0, "unknown option: -bad"},
 		},
 	}
 	for _, c := range cases {
@@ -35,7 +35,7 @@ func TestUnknown(t *testing.T) {
 			t.Errorf("ParseOsArgs %q != %q", gotOptionValue, c.want.value)
 		} else if gotChomped != c.want.chomped {
 			t.Errorf("ParseOsArgs %q != %q", gotChomped, c.want.chomped)
-		} else if gotError.Error() != c.want.errorMessage {
+		} else if gotError != nil && gotError.Error() != c.want.errorMessage {
 			t.Errorf("ParseOsArgs %q != %q", gotError.Error(), c.want.errorMessage)
 		}
 	}