doc: use version 1.0.0 in crate doc example

KiChjang · BurntSushi · commit ba874953aaed · 2018-05-08T07:00:47.000-04:00
diff --git a/src/lib.rs b/src/lib.rs
@@ -29,7 +29,7 @@ used by adding `regex` to your dependencies in your project's `Cargo.toml`.
 
 ```toml
 [dependencies]
-regex = "0.2"
+regex = "1.0.0"
 ```
 
 and this to your crate root:
