v0.4.0 - big perf improvements!

Thanks to Jørgen P. Tjernø for the work to skip the long file copy and instead of relying on revert, relying on fstat and perforce digests to save a ton of time.

Note that starting with this release, when p4harmonize is done, the local folder that is created for the destination workspace will no longer contain ALL files, and instead will only contain the files that are new or have changed. Once you submit the generated changelist, that folder and the corresponding workspace should probably be deleted to avoid confusion, since to actually use that folder you'd need to force sync down all the files that are missing.

A future release might want to have options to include the submit and cleanup steps so the user doesn't have to do that manually.