docs(readme): create rudimentary README.md

Author: aqrln

README.md

@@ -0,0 +1,21 @@
+# Node.js N-API for Rust! [work in progress]
+
+[![Build Status][travis-badge]][travis-url]
+
+## Crates
+
+* `napi-sys`: low-level bindings to N-API generated from
+  [`node_api.h`](https://github.com/nodejs/node/blob/master/src/node_api.h)
+  using [`bindgen`](https://github.com/rust-lang-nursery/rust-bindgen).
+* `napi`: high-level and rusty wrappers around `napi-sys`.
+* `napi-codegen`: a compiler plugin designed for you to be able to write a
+  regular Rust function that takes JavaScript values as arguments and returns a
+  `NapiResult`, put an annotation, and be good to go.  It's not clear at this
+  point whether we will continue taking this route, though.  On the second
+  thought, pretty function signatures don't seem worth diving into the hassle
+  of maintaining compatibility with the latest nightly compiler and requiring
+  using it.  Good old macros and just a little bit of boilerplate code will
+  solve the problem as well.
+
+[travis-badge]: https://travis-ci.org/aqrln/napi-rs.svg?branch=master
+[travis-url]: https://travis-ci.org/aqrln/napi-rs