Setup yasnippet

Don't add yasnippet-snippets; hopefully most of the snippets will come from
language servers.

Also make sure that company-yasnippet is available, to make sure that snippets
are at least somewhat discoverable.

modules/development/snippets/python-mode/class

@@ -0,0 +1,14 @@
+# -*- mode: snippet -*-
+# name: new class
+# key: class
+# --
+class $1:
+    """
+    $2
+    """
+    def __init__(self${3:, *args, **kwargs}):
+        """
+        $4
+        """
+        ${0:pass}
+