Add basic ID3v1 support and set size of covers

Dear,

Would you please merge this branch toward your main git repo?
- It fixes the issue #7 (exception when used with param -t),
- adds id3v1 tags at the end of the mp3 file in read function (issue #9), this is basic now (author, album and comment are added, no genre nor year).
- fetch the size of the cover files if the -t option is used.

Best regards, henry-nicolas