updates header with modern society

Author: kjaymiller

_includes/header.html

@@ -1,6 +1,6 @@
 {% assign t = site.data.locales[page.lang][page.lang] %}
 <header class="site-header" role="banner">
-  <h1 class="site-title"><a class="logo-text" href="/index.html"><img src="{{ '/assets/images/black_python_devs_logo.svg' | relative_url }}" alt="Black Python Devs" /></a></h1>
+  <h1 class="site-title"><a class="logo-text" href="/index.html"><img src="{{ 'assets/images/black_python_devs_logo-horizontal-white.png' | relative_url }}" alt="Black Python Devs" /></a></h1>
   <nav class="site-navigation">
     <div class="site-navigation-wrap">
       <ul class="menu" role="menu">