add installation instructions (#110)

Signed-off-by: Lucas Larson <[email protected]>

Author: LucasLarson

readme.adoc

@@ -100,7 +100,7 @@ plugin^] or you can just clone this repository, run the following command, and
 then restart your terminal:
 [source,zsh]
 $ printf '%s\n' '. /path/to/gunstage.plugin.zsh' \
-  >>"${HOME-}"'/.'"${SHELL##*[-./]}"'rc'
+  >>"$(printf '%s\n' "${HOME-}"'/.'"${SHELL##*[-./]}"'rc')"
 
 Requirements
 ~~~~~~~~~~~~