Check each ID3 tag is valid.

Some tag encoders like to use non-standard padding (see http://id3.org/Compliance%20Issues) which was causing "unexpected EOF" errors.  Checking that each tag has a valid name (as per the spec) seems to be the only good way around this.

id3v2.go

@@ -167,6 +167,12 @@ func readID3v2Frames(r io.Reader, h *ID3v2Header) (map[string]interface{}, error
 			return nil, err
 		}
 
+		// Avoid corrupted padding (see http://id3.org/Compliance%20Issues).
+		if !validID3Frame(h.Version, name) {
+			break
+		}
+
+		// FIXME: Do we still need this?
 		// if size=0, we certainly are in a padding zone. ignore the rest of
 		// the tags
 		if size == 0 {