Suggest shallow git clone for regular usage

Avoid copy useless files (download+storage)

Author: ajoga

README.md

@@ -43,7 +43,7 @@ include ::tfenv
 1. Check out tfenv into any path (here is `${HOME}/.tfenv`)
 
 ```console
-$ git clone https://github.com/tfutils/tfenv.git ~/.tfenv
+$ git clone --depth=1 https://github.com/tfutils/tfenv.git ~/.tfenv
 ```
 
 2. Add `~/.tfenv/bin` to your `$PATH` any way you like