RFC 70 is error interoperation

Author: alexcrichton

active/0000-error-chaining.md renamed to active/0070-error-chaining.md

@@ -1,6 +1,6 @@
 - Start Date: (fill me in with today's date, 2014-07-17)
-- RFC PR #: (leave this empty)
-- Rust Issue #: (leave this empty)
+- RFC PR #: [rust-lang/rfcs#201](https://github.com/rust-lang/rfcs/pull/201)
+- Rust Issue #: [rust-lang/rust#17747](https://github.com/rust-lang/rust/issues/17747)
 
 # Summary