Add some feature gates

Author: alexcrichton

.gitignore

@@ -1,3 +1,3 @@
-/target
-/Cargo.lock
+target
+Cargo.lock
 src/main.rs

libgit2-sys/build.rs

@@ -1,4 +1,4 @@
-#![allow(unstable)]
+#![feature(path, io, os, core, collections)]
 
 extern crate "pkg-config" as pkg_config;
 

src/lib.rs

@@ -66,11 +66,10 @@
 //! source `Repository`, to ensure that they do not outlive the repository
 //! itself.
 
-#![feature(unsafe_destructor)]
+#![feature(unsafe_destructor, hash, std_misc, core, collections, path)]
+#![feature(io)]
 #![deny(missing_docs)]
 #![cfg_attr(test, deny(warnings))]
-#![cfg_attr(test, allow(unstable))]
-#![allow(unstable)]
 
 extern crate libc;
 extern crate url;