Working on how to actually write the archive.

Made SuperblockFlags public so you can set options when writing

bufferedwriter.go

@@ -0,0 +1,15 @@
+package squashfs
+
+import (
+	"io"
+)
+
+type bufferedWriter struct {
+	w      io.Writer
+	buffer []bufferedBytes
+}
+
+type bufferedBytes struct {
+	data   []byte
+	offset int
+}