tokio-fs: Add async versions of most of std::fs (#494)

* create_dir
* create_dir_all
* hard_link
* read_dir
* read_link
* remove_dir
* remove_file
* rename
* set_permissions that works with path
* symlink_metadata
* symlink on unix
* symlink_dir on windows
* symlink_file on windows

tokio-fs/src/create_dir.rs

@@ -0,0 +1,46 @@
+use std::fs;
+use std::io;
+use std::path::Path;
+
+use futures::{Future, Poll};
+
+/// Creates a new, empty directory at the provided path
+///
+/// This is an async version of [`std::fs::create_dir`][std]
+///
+/// [std]: https://doc.rust-lang.org/std/fs/fn.create_dir.html
+pub fn create_dir<P: AsRef<Path>>(path: P) -> CreateDirFuture<P> {
+    CreateDirFuture::new(path)
+}
+
+/// Future returned by `create_dir`.
+#[derive(Debug)]
+pub struct CreateDirFuture<P>
+where
+    P: AsRef<Path>
+{
+    path: P,
+}
+
+impl<P> CreateDirFuture<P>
+where
+    P: AsRef<Path>
+{
+    fn new(path: P) -> CreateDirFuture<P> {
+        CreateDirFuture {
+            path: path,
+        }
+    }
+}
+
+impl<P> Future for CreateDirFuture<P>
+where
+    P: AsRef<Path>
+{
+    type Item = ();
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        ::blocking_io(|| fs::create_dir(&self.path) )
+    }
+}