Add path.parse, path.format

[chrisdickinson]

Continuing from #7429.

The feature was originally given the go-ahead by @isaacs.
@roryrjb opened a pr that stalled -- I'm reopening this, having fixed the style issues.

Tested on Win7 + OSX 10.10.

/cc @tjfontaine @indutny

path.parse

Returns an object from a path string.

An example on *nix:

path.parse('/home/user/dir/file.txt')
// returns
{
    root : "/",
    dir : "/home/user/dir",
    base : "file.txt",
    ext : ".txt",
    name : "file"
}

An example on Windows:

path.parse('C:\\path\\dir\\index.html')
// returns
{
    root : "C:\",
    dir : "C:\path\dir",
    base : "index.html",
    ext : ".html",
    name : "index"
}

path.format

Returns a path string from an object, the opposite of path.parse above.

path.format({
    root : "/",
    dir : "/home/user/dir",
    base : "file.txt",
    ext : ".txt",
    name : "file"
})
// returns
'/home/user/dir/file.txt'

[othiym23]

This is a very useful concept and I would use the heck out of it if it were in Node.

[tjfontaine]

From the irc conversation, I am +1 on this, and would like to see it rebased on top of https://github.com/misterdjules/node/compare/joyent:v0.12...path-platform?w=1 which reorders the path module to expose platform based semantics -- re #5661

[chrisdickinson]

Merged in 2d17193.