Create 2014-08-04-spree-girls-blog-post.md

Adding Tracy Mu Sung and Catherine Jones' blog post for Spree Girls
Maybe explicitely state the term »voluntary team« and link to http://railsgirlssummerofcode.org/blog/everything-you-ever-wanted-to-know-about-volunteer-teams/ and/or http://railsgirlssummerofcode.org/blog/final-team-list-2014/#volunteering-teams ?