Rename getgb plugin to gb

plugins/getgb/README.md → plugins/gb/README.md

@@ -9,9 +9,9 @@ See https://getgb.io for the full `gb` documentation
 - Adds completion support for all `gb` commands.
 - Also supports completion for the [`gb-vendor` plugin](https://godoc.org/github.com/constabulary/gb/cmd/gb-vendor).
 
-To use it, add `getgb` to your plugins array:
+To use it, add `gb` to your plugins array:
 ```sh
-plugins=(... getgb)
+plugins=(... gb)
 ```
 
 ## Caveats