Upgrade installation docs

Author: dylanhitt

README.md

@@ -10,7 +10,7 @@ A simple package to execute shell commands on linux, darwin and windows.
 
 ## Installation
 
-`$ go get -u github.com/commander-cli/cmd@v1.0.0`
+`$ go get -u github.com/commander-cli/cmd@v1.5.0`
 
 ## Usage