SEO Changes

Enhanced title & h1, added h2, added size parameter to img src path,
added alt tag. Created (basic) robots.txt & sitemap.xml
I'm not totally sure about putting Hire in the title like this.  I see how it could be smart from an SEO perspective b/c that's an important keyword.  But a lot of the people who have signed up have done so thinking that it's not primarily a hiring board.  I'd feel more comfortable optimizing for "magento developer" as opposed to "hire magento developer".