s/Nicholas/Niko/ on the new post

I think I'd prefer to go by Nicholas in contexts like these.

Author: nikomatsakis

posts/inside-rust/2019-09-25-Welcome.md

@@ -1,7 +1,7 @@
 ---
 layout: post
-title: "Announcing the Inside Rust blog!"
-author: Niko Matsakis
+title: "Welcome to the Inside Rust blog!"
+author: Nicholas Matsakis
 description: "A new blog where the Rust team can post updates on the latest developments"
 team: the core team <https://www.rust-lang.org/governance/teams/core>
 ---