Restore file mtimes after modification

[GoogleCodeExporter]

Especially when doing a "beets update", but also with other operations 
involving just updating the tags instead of the audio data of a file, it would 
be great if there was an option to preserve the file modification times, so 
that players that use file modification times wouldn't detect the files as new 
additions.

The feature could be implemented simply by doing a 

    filetimes = os.stat(file)

before writing out the metadata, and a

    os.utime(file, filetimes)

after writing it.

Original issue reported on code.google.com by julf.helsingius on 30 Sep 2012 at 7:14

[untitaker]

Do not comment here, but on beetbox/beets#146