Google or other search engine go to the sitemap.xml after every few hours so if your sitemap.xml is updated then there is no need to submit URL explicitly. From QueryHome we have seen most of the time URL is on Google within one hours and we don't submit any URL explicitly.
Consider the addition of lastmod in the sitemap.xml like
<loc>
http://tech.queryhome.com/19/can-make-codesniffer-fixer-ignore-the-namespace-declaration
</loc>
<priority>0.1009007207605</priority>
<changefreq>daily</changefreq>
<lastmod>2013-03-12T16:50:04+00:00</lastmod>