Thefuck: homebrew install documentation and thefuck repo link (#5940)

* Thefuck: homebrew install documentation and thefuck repo link
* thefuck: reformat error message

plugins/thefuck/thefuck.plugin.zsh

 if [[ -z $commands[thefuck] ]]; then
-    echo 'thefuck is not installed, you should "pip install thefuck" first'
-    return -1
+    echo 'thefuck is not installed, you should "pip install thefuck" or "brew install thefuck" first.'
+    echo 'See https://github.com/nvbn/thefuck#installation'
+    return 1
 fi
 
 # Register alias