Code52/pretzel — pull request #162 by dubeaud (2013-11-27 20:39:46+00:00)
Title: added date_to_xmlschema filter to liquid engine

dotLiquid does not include the date_to_xmlschema that the atom.liquid template uses.

This pull request adds the date_to_xmlschema filter and aligns pretzel with jekyll's template offerings
```
{{ site.time | date_to_xmlschema }}
2008-11-07T13:07:54-08:00
```