Changes date interpretation to assume UTC in blog example

To test this fix, switch your computer's timezone to PST (or something in the U.S.) and generate the blog before and after this fix.  Before the fix, the 'Red Herring' article will be displayed as '31. March 2013' , instead of '01. april 2013' in the articles, and categorized as March 2013 in the archive.


@jnordberg - I made this fix without fully rebuilding Wintersmith locally, but rather copied the fix from the generated blog template.  I'm having some trouble installing npm with the --dev flag (new to NPM development).   

...#113