Parsing mode from string already in node's lib.js

Hello,

Node's fs.mkdir and fs.mkdirSync already call an internal modeNum method to parse the mode from string type.  Therefore it is unneeded in this lib.

See: https://github.com/joyent/node/blob/master/lib/fs.js#L324

Thanks!

**Charles**
Use https, not http, for Github repo URL
0.4.2