Added meta description (#101)

Added meta description to help with SEO results

layouts/_sitehead.html

@@ -5,6 +5,7 @@
   <meta http-equiv="Content-Language" content="en-us" />
   <meta name="robots" content="all" />
   <meta name="viewport" content="width=device-width, initial-scale=1" />
+  <meta name="description" content="The Bioconductor project aims to develop and share open source software for precise and repeatable analysis of biological data. We foster an inclusive and collaborative community of developers and data scientists." />
 
   <% if item.identifier =~ /^\/help\/bioc-views\/package-pages\// and not
   item.identifier =~ /\/all-/ %>
@@ -48,4 +49,4 @@
   <link rel="ICON" type="image/x-icon" href="/favicon.ico" />
 
 
-</head>
+</head>