Async Walker

This is just a basic async walker that allows you to perform manipulation (read: filter, map) during a file walk. It's fully async and returns a Q promise.

Note:
If you're looking for something to do glob matching, this isn't the implementation you want. Check out node-glob, which is a very comprehensive and solid implementation.

Usage

$3

Find all files: Passing a path to async-walker results in a promise w/ an array of files qualified to the base path.
``js
var walker = require('async-walker');
walker('./path/').then(function(files) {
console.log(files); // => Files array: ['./path/to/file.js']
});
`

With callback: The callback approach passes an object for each item that contains the path and two fs.stat properties: isDirectory and isFile. These are boolean values (not functions).

You're required to return a statObject or something falsey. Returning falsey values means the object's path will not be included in the result or be walked further).

Note: This is a synchronous operation. It could be made async later.
`js
walker('./path', function(statObject) {
var filePath = statObject.path;

if (statObject.isFile && filePath.substr(-3) == '.js') {
var file = fs.readFile(filePath, function(err, contents) {
// Do something w/ javascript file contents
});
}

return statObject;
});
`

$3

#### Walker.filter(path, callback, [matchDirectories])
Takes a path to walk, and a callback, the boolean results of which will determine whether the item will be included. Optionally, a matchDirectories param can be added to specify whether to apply the filter callback to directories (defaults to false).

`js
walker.filter('./node_modules', function(item) {
return /readme\.{2,3}/i.test(item);
}).then(function(readmes) {
// => Do something w/ all readme files in node_modules
});
`

#### Walker.map(path, callback)
Applies a the result of a map function to each file. This does not deal w/ directories at all. I'm not sure why you'd use this, but I added to test the implementation.

`js
walker.map('./path', function(item) {
return item.toUpperCase();
}).then(function(files) {
console.log(files); // => [./PATH/TO/FILE.JS...]
});
``