Enhanced stat object

[phated]

Opening this as the solution to a bunch of other issues.

This to achieve:

• *nix-like behavior for atime/mtime/etc properties (#72)
• Virtual directories (#100)
• User-friendly mode property (gulpjs/vinyl-fs#112)
• Construct with always-valid properties (new fs.Stats doesn't do this)
• Flag remote files (isRemote) and avoid path normalization or do URI normalization (#127)
• More?