[autosuggestions] Add module

Closes #172. Fixes #35.

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "modules/prompt/external-themes/lean"]
 	path = modules/prompt/external-themes/lean
 	url = https://github.com/miekg/lean
+[submodule "modules/autosuggestions/external"]
+	path = modules/autosuggestions/external
+	url = https://github.com/zsh-users/zsh-autosuggestions.git

modules/autosuggestions/README.md

@@ -0,0 +1,13 @@
+zsh-autosuggestions
+===================
+
+_[Fish](http://fishshell.com/)-like fast/unobtrusive autosuggestions for zsh._
+
+It suggests commands as you type, based on command history.
+
+<a href="https://asciinema.org/a/37390" target="_blank"><img src="https://asciinema.org/a/37390.png" width="400" /></a>
+
+Contributing
+------------
+
+Contributions should be submitted [upstream to zsh-autosuggestions](https://github.com/zsh-users/zsh-autosuggestions)

modules/autosuggestions/external

@@ -0,0 +1 @@
+Subproject commit fedc22e9bbd046867860e772d7d6787f5dae9d4c

modules/autosuggestions/init.zsh

@@ -0,0 +1,9 @@
+#
+# Fish-like fast/unobtrusive autosuggestions for zsh.
+#
+# It suggests commands as you type, based on command history.
+#
+
+# source script
+source ${0:h}/external/zsh-autosuggestions.zsh || return 1
+