Filter out directory paths for FileFinder in Objective-C instead of JS.

Rename FileSystemHelper-contentsOfDirectoryAtPath… to -listFilesAtPath to make it clear that we're only listing files, not subdirectories. This is a fairly special purpose method but it saves us from calling back into objective-c a ton of times to filter them in JS, and makes bringing up the file finder ~2x as fast.

src/atom/project.coffee

@@ -7,7 +7,6 @@ class Project
 
   getFilePaths: ->
     projectUrl = @url
-    fs.async.list(@url, true).pipe (urls) ->
-      urls = (url.replace(projectUrl, "") for url in urls when fs.isFile(url))
-      urls
+    fs.async.listFiles(@url, true).pipe (urls) ->
+      url.replace(projectUrl, "") for url in urls
 

src/stdlib/fs.coffee

@@ -42,7 +42,7 @@ module.exports =
   # Returns true if the file specified by path exists and is a
   # regular file.
   isFile: (path) ->
-    $atomController.isFile path
+    $atomController.fs.isFile path
 
   # Returns an array with all the names of files contained
   # in the directory path.
@@ -87,9 +87,9 @@ module.exports =
     OSX.NSFileManager.defaultManager.currentDirectoryPath.toString()
 
   async:
-    list: (path, recursive) ->
+    listFiles: (path, recursive) ->
       deferred = $.Deferred()
-      $atomController.fs.contentsOfDirectoryAtPath_recursive_onComplete path, recursive, (subpaths) ->
+      $atomController.fs.listFilesAtPath_recursive_onComplete path, recursive, (subpaths) ->
         deferred.resolve subpaths
       deferred