Add fasd as an external module

.gitmodules

@@ -19,3 +19,6 @@
 [submodule "modules/prompt/functions/pure"]
 	path = modules/prompt/external/pure
 	url = https://github.com/sindresorhus/pure.git
+[submodule "modules/fasd/external"]
+	path = modules/fasd/external
+	url = https://github.com/clvv/fasd

modules/fasd/external

@@ -0,0 +1 @@
+Subproject commit 90b531a5daaa545c74c7d98974b54cbdb92659fc

modules/fasd/init.zsh

@@ -9,10 +9,8 @@
 # Load dependencies.
 pmodload 'editor'
 
-# Return if requirements are not found.
+# Source module file.
-if (( ! $+commands[fasd] )); then
+source "${0:h}/external/fasd" || return 1
-  return 1
-fi
 
 #
 # Initialization