Readme : use cargo install

Author: Tristramg

readme.md

@@ -7,4 +7,4 @@ It converts an OpenStreetMap file (in the `.pbf` format) into a CSV file.
 ## Build
 Get a rust distribution with `cargo`: https://www.rust-lang.org/en-US/downloads.html
 
-Run `cargo build`
+Run `cargo install osm4routing`