Add links to impl period blog post and gitter.im

Author: pepyakin

README.md

@@ -1,5 +1,7 @@
 # `bindgen`
 
+[`impl period`](https://blog.rust-lang.org/2017/09/18/impl-future-for-rust.html) has been started! Join us at [Gitter.im](https://gitter.im/rust-impl-period/WG-dev-tools-bindgen).
+
 **`bindgen` automatically generates Rust FFI bindings to C and C++ libraries.**
 
 For example, given the C header `doggo.h`: