Merge pull request #3 from CNG/master

Reference AssetFilename for sites with linked assets. Resolves Issue 2

wxr.mhtml

@@ -171,7 +171,7 @@
     <wp:post_id><$mt:AssetID encode_xml="1"$></wp:post_id>
     <wp:post_date><$mt:AssetDateAdded format="%Y-%m-%d %H:%M:%S" encode_xml="1"$></wp:post_date>
     <wp:post_date_gmt><$mt:AssetDateAdded format="%Y-%m-%d %H:%M:%S" utc="1" encode_xml="1"$></wp:post_date_gmt>
-    <wp:post_name><$mt:PageBasename separator="-" encode_xml="1"$></wp:post_name>
+    <wp:post_name><$mt:AssetFilename encode_xml="1"$></wp:post_name>
     <wp:status>inherit</wp:status>
     <wp:post_parent>0</wp:post_parent>
     <wp:menu_order>0</wp:menu_order>