WIP: MsgPack stubs, Level Filesystem Module

* Add some encoding/decoding functions for binary msgpack format for
  levels and doodads. Currently it writes msgpack files that can be
  decoded and printed by Python (mp2json.py) but it can't re-read from
  the binary format. For now, levels will continue to write in JSON
  format.
* Add filesystem abstraction functions to the balance/ package to search
  multiple paths to find Levels and Doodads, to make way for
  system-level doodads.

color.go

@@ -7,6 +7,8 @@ import (
 	"image/color"
 	"regexp"
 	"strconv"
+
+	"github.com/vmihailenco/msgpack"
 )
 
 var (
@@ -155,6 +157,52 @@ func (c *Color) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
+func (c Color) EncodeMsgpack(enc *msgpack.Encoder) error {
+	return enc.EncodeString(fmt.Sprintf(
+		`"#%02x%02x%02x"`,
+		c.Red, c.Green, c.Blue,
+	))
+}
+
+func (c Color) DecodeMsgpack(dec *msgpack.Decoder) error {
+	hex, err := dec.DecodeString()
+	if err != nil {
+		return fmt.Errorf("Color.DecodeMsgpack: %s", err)
+	}
+
+	parsed, err := HexColor(hex)
+	if err != nil {
+		return fmt.Errorf("Color.DecodeMsgpack: HexColor: %s", err)
+	}
+
+	c.Red = parsed.Red
+	c.Blue = parsed.Blue
+	c.Green = parsed.Green
+	c.Alpha = parsed.Alpha
+	return nil
+}
+
+// // MarshalMsgpack serializes the Color for msgpack.
+// func (c Color) MarshalMsgpack() ([]byte, error) {
+// 	data := []uint8{
+// 		c.Red, c.Green, c.Blue, c.Alpha,
+// 	}
+// 	return msgpack.Marshal(data)
+// }
+//
+// // UnmarshalMsgpack decodes a Color from msgpack format.
+// func (c *Color) UnmarshalMsgpack(b []byte) error {
+// 	var data []uint8
+// 	if err := msgpack.Unmarshal(data, b); err != nil {
+// 		return err
+// 	}
+// 	c.Red = 255
+// 	c.Green = data[1]
+// 	c.Blue = data[2]
+// 	c.Alpha = data[3]
+// 	return nil
+// }
+
 // Add a relative color value to the color.
 func (c Color) Add(r, g, b, a int) Color {
 	var (