update to use new io.Seek consts, require min go1.7

id3v1.go

@@ -7,7 +7,6 @@ package tag
 import (
 	"errors"
 	"io"
-	"os"
 	"strconv"
 	"strings"
 )
@@ -44,7 +43,7 @@ var ErrNotID3v1 = errors.New("invalid ID3v1 header")
 // ReadID3v1Tags reads ID3v1 tags from the io.ReadSeeker.  Returns ErrNotID3v1
 // if there are no ID3v1 tags, otherwise non-nil error if there was a problem.
 func ReadID3v1Tags(r io.ReadSeeker) (Metadata, error) {
-	_, err := r.Seek(-128, os.SEEK_END)
+	_, err := r.Seek(-128, io.SeekEnd)
 	if err != nil {
 		return nil, err
 	}