Add Elixir with clause snippets

This is an addition to Elixir's syntax as of version 1.2.0 which wasn't
yet included in the current snippet list.

Author: Auralcat

snippets/elixir-mode/wt

@@ -0,0 +1,8 @@
+# -*- mode: snippet -*-
+# contributor: Miriam Retka (https://github.com/Auralcat)
+# name: wt
+# key: wt
+# --
+with ${1:{:ok, tuple} <- function(arg)}, do
+  $0
+end

snippets/elixir-mode/wte

@@ -0,0 +1,10 @@
+# -*- mode: snippet -*-
+# contributor: Miriam Retka (https://github.com/Auralcat)
+# name: wte
+# key: wte
+# --
+with ${1:{:ok, tuple} <- function(arg)}, do
+  $2
+else
+  $0
+end