Fix typo in readme.md

Author: NReilingh

README.md

@@ -15,7 +15,7 @@ that suspends and archives a folder of VMs to dmg.
 
 This code has unit tests! Get ZUnit with
 
-    brew install zunit-zsh/zunit/zunit`
+    brew install zunit-zsh/zunit/zunit
 
 and then run `zunit` in the project directory to test.