integrated screenshot in readme

themes/bira/README.md

+## bira
+
+Theme imported from Oh my ZSH: https://github.com/robbyrussell/oh-my-zsh/blob/master/themes/bira.zsh-theme
+Contains traces of nuts and code from other Oh my fish themes.
+
+Display username, hostname, current path and git status:
+
+![bira theme](https://raw.github.com/vincent-psarga/oh-my-fish/master/themes/bira/screenshot.png)
+
+TODO:
+ - display latest return code
+ - display Ruby version
+ - display Python version