add migration from versions 0.3.3, 0.3.4, 0.3.5 (#3)

cmd/migration-tool/log.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"log"
+	"os"
+)
+
+type Logger struct {
+	DebugMode bool
+
+	_debug *log.Logger
+	_info  *log.Logger
+	_error *log.Logger
+}
+
+func NewLogger() *Logger {
+	return &Logger{
+		DebugMode: false,
+		_debug:    log.New(os.Stdout, "DEBUG: ", 0),
+		_info:     log.New(os.Stdout, "", 0),
+		_error:    log.New(os.Stderr, "ERROR: ", 0),
+	}
+}
+
+func (l *Logger) Debug(format string, v ...interface{}) {
+	if l.DebugMode {
+		l._debug.Printf(format, v...)
+	}
+}
+
+func (l *Logger) Info(format string, v ...interface{}) {
+	l._info.Printf(format, v...)
+}
+
+func (l *Logger) Error(format string, v ...interface{}) {
+	l._error.Printf(format, v...)
+}