Setup for differnet types of compression for Writer

Added some TODOs

writer_compression_options.go

@@ -0,0 +1,15 @@
+package squashfs
+
+//TODO: Allow settings the options
+
+// func (w *Writer) SetGzipOptions() error {}
+
+// func (w *Writer) SetLzmaOptions() error {}
+
+// func (w *Writer) SetLzoOptions() error {}
+
+// func (w *Writer) SetXzOptions() error {}
+
+// func (w *Writer) SetLz4Options() error {}
+
+// func (w *Writer) SetZstdOptions() error {}