Adding site map generation #185

using the sitemap_generator gem, trigger daily by clock, generated in a sidekiq worker
Some example output
```
This XML file does not appear to have any style information associated with it. The document tree is shown below.
<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:image="http://www.google.com/schemas/sitemap-image/1.1" xmlns:video="http://www.google.com/schemas/sitemap-video/1.1" xmlns:geo="http://www.google.com/geo/schemas/sitemap/1.0" xmlns:news="http://www.google.com/schemas/sitemap-news/0.9" xmlns:mobile="http://www.google.com/schemas/sitemap-mobile/1.0" xmlns:pagemap="http://www.google.com/schemas/sitemap-pagemap/1.0" xmlns:xhtml="http://www.w3.org/1999/xhtml" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
<url>
<loc>https://test.com</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>always</changefreq>
<priority>1.0</priority>
</url>
<url>
<loc>https://test.com/welcome</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>montlhy</changefreq>
<priority>0.7</priority>
</url>
<url>
<loc>https://test.com/contact_us</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>montlhy</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/blog</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.7</priority>
</url>
<url>
<loc>https://test.com/api</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/faq</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/privacy_policy</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.2</priority>
</url>
<url>
<loc>https://test.com/tos</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.2</priority>
</url>
<url>
<loc>https://test.com/jobs</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>daily</changefreq>
<priority>0.7</priority>
</url>
<url>
<loc>https://test.com/employers</loc>
<lastmod>2014-09-25T16:53:37+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.7</priority>
</url>
<url>
<loc>https://test.com/p/lwl_wq</loc>
<lastmod>2014-09-25T02:34:32+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/p/yug7ha</loc>
<lastmod>2014-09-25T02:34:33+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/p/-xrl3q</loc>
<lastmod>2014-09-25T02:34:33+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/team/put-a-bird-on-it</loc>
<lastmod>2014-09-25T02:34:34+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/team/team-awesome</loc>
<lastmod>2014-09-25T02:00:30+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/team/team-wonderful</loc>
<lastmod>2014-09-25T02:28:58+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/team/parker-dibbert</loc>
<lastmod>2014-09-25T02:31:33+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/team/glamouros</loc>
<lastmod>2014-09-25T02:52:01+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>
https://test.com/team/glamouros/Manger-of-Cool-wrfhdg
</loc>
<lastmod>2014-09-25T02:52:01+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/bryce</loc>
<lastmod>2014-09-25T02:34:34+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/lisa</loc>
<lastmod>2014-09-25T02:34:34+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/testser</loc>
<lastmod>2014-09-25T04:52:54+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/blog/2012-02-23-hating-on-IE6</loc>
<lastmod>2012-02-23T21:37:05-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>
https://test.com/blog/2012-02-05-the-companies-id-want-to-work-for
</loc>
<lastmod>2012-02-05T20:55:47-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>
https://test.com/blog/2012-01-16-the-hacker-version-of-an-embeddable-social-button
</loc>
<lastmod>2012-01-16T11:02:41-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>
https://test.com/blog/2012-01-10-represent-get-geek-cred-on-your-blog
</loc>
<lastmod>2012-01-10T12:04:36-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>
https://test.com/blog/2012-01-09-starting-off-the-new-year-with-a-bang
</loc>
<lastmod>2012-01-09T14:25:31-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://test.com/blog/2011-07-22-gaming-the-game</loc>
<lastmod>2011-07-22T00:09:00-08:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.5</priority>
</url>
</urlset>
```
@seuros @just3ws I don't believe anything is persisted between dynos. 

From https://devcenter.heroku.com/articles/how-heroku-works: "Changes to the filesystem on one dyno are not propagated to other dynos and are not persisted across deploys and dyno restarts." 

Also, from https://devcenter.heroku.com/articles/dynos#isolation-and-security "Ephemeral File System":
Each dyno gets its own ephemeral filesystem, with a fresh copy of the most recently deployed code. During the dyno’s lifetime its running processes can use the filesystem as a temporary scratchpad, but no files that are written are visible to processes in any other dyno and any files written will be discarded the moment the dyno is stopped or restarted.