Add syntax for version numbers

[brendanberg]

As part of the header separator?

1.0=

=1.0

[brendanberg]

Alternately, the first line could specify the version info:

tablo/1.0
"Artist", "Album", "Song", "Downloads"
=

If a file does not have a version specifier, it is interpreted as the latest version the parser can read. If a file does have a version specifier, parser behavior depends on whether the file's version is newer or older than the parser's version. A parser with a version older than the file's version should not parse the file. (An optional flag to attempt parsing in a compatibility mode may be used.) A parser newer than the file's version should parse the file using the parsing rules from the older version of the format.