Tighten module requirements

Use Mojo 4.0 or newer.  Fixes #2.

Signed-off-by: Zak B. Elep <zakame@zakame.net>
Checking in changes prior to tagging of version 2.04.

Changelog diff is:

diff --git a/Changes b/Changes
index 1f34b45..41eb91d 100644
--- a/Changes
+++ b/Changes
@@ -3,6 +3,9 @@ MojoX-Renderer-WriteExcel)

 {{$NEXT}}

+2.04 2014-12-10T07:48:21Z
+        Require Mojo 4.0 or newer, Closes #2
+
 2.03 2014-12-08T10:05:37Z
         Remove use of Mojo::IOLoop for test, Closes #1
         Switch build to Minilla