Vendor dependencies for 0.3.0 release

vendor/num-traits/build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let ac = autocfg::new();
+
+    ac.emit_expression_cfg("1f64.total_cmp(&2f64)", "has_total_cmp"); // 1.62
+
+    autocfg::rerun_path("build.rs");
+}