refactor: move tunnel pkg down one level (#358)

* refactor: move tunnel pkg down one level

While there, reduce unnecessary dependency on external packages.

* file I forgot to commit

internal/tunnel/config_test.go

@@ -0,0 +1,36 @@
+package tunnel
+
+import (
+	"testing"
+
+	"github.com/apex/log"
+)
+
+func TestConfigLoggerDefault(t *testing.T) {
+	config := &Config{}
+	if config.logger() != defaultLogger {
+		t.Fatal("not the logger we expected")
+	}
+}
+
+func TestConfigLoggerCustom(t *testing.T) {
+	config := &Config{Logger: log.Log}
+	if config.logger() != log.Log {
+		t.Fatal("not the logger we expected")
+	}
+}
+
+func TestTorBinaryNotSet(t *testing.T) {
+	config := &Config{}
+	if config.torBinary() != "tor" {
+		t.Fatal("not the result we expected")
+	}
+}
+
+func TestTorBinarySet(t *testing.T) {
+	path := "/usr/local/bin/tor"
+	config := &Config{TorBinary: path}
+	if config.torBinary() != path {
+		t.Fatal("not the result we expected")
+	}
+}