impl $attr->default($instance) for compatibility with Moose

for:
    https://github.com/schwern/sqitch/commit/3a2971c1d57bd3159c6cb785cc776f3169612730
add a test file
Checking in changes prior to tagging of version 1.04.

Changelog diff is:

diff --git a/Changes b/Changes
index e165db5..077ef68 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,9 @@
 Revision history for Mouse

+1.04 2013-01-11 01:46:18
+    [FEATURES]
+    - Implement $attr->default($instance) for compatibility with Moose
+
 1.03 2013-01-11 01:10:38
     [FEATURES]
     - Add maybe_type() from Moose::Util::TypeConstraints (schwern)