Minor doc updates to codegen readme

Author: sgrif

diesel_codegen/README.md

@@ -9,11 +9,11 @@ boilerplate needing to be written. It can be used through `rustc_plugin`, or
 Using on nightly
 ----------------
 
-Make sure you're on a nightly from 2016-01-23 or later, we don't compile on earlier versions. To use with nightly, you'll want to turn off the default features. Add this
+Make sure you're on a nightly from 2016-03-11 or later, we don't compile on earlier versions. To use with nightly, you'll want to turn off the default features. Add this
 line to your dependencies section in `Cargo.toml`
 
 ```toml
-diesel_codegen = { version = "0.5.0", default-features = false, features = ["nightly"] }
+diesel_codegen = { version = "0.5.0", default-features = false, features = ["nightly", "postgres"] }
 ```
 
 Then you'll need to add two lines to the root of your crate.