Fix reading UInt32

In JS, 0x80 << 24 yields a negative result.  Also, 0x80000000|0 < 0.
Bitwise ops should be avoided for very long unsigned ints.

lib/data.coffee

@@ -19,11 +19,11 @@ class Data
     @writeByte if val then 1 else 0
     
   readUInt32: ->
-    b1 = @readByte() << 24
+    b1 = @readByte() * 0x1000000
     b2 = @readByte() << 16
     b3 = @readByte() << 8
     b4 = @readByte()
-    b1 | b2 | b3 | b4
+    b1 + b2 + b3 + b4
   
   writeUInt32: (val) ->
     @writeByte (val >>> 24) & 0xff
@@ -137,4 +137,4 @@ class Data
     for byte in bytes
       @writeByte byte
     
-module.exports = Data
+module.exports = Data