fixed typo, docs on large displays and changed travis to bionic dist

docs/assets/css/default.css

@@ -5,6 +5,8 @@ body {
   background: #00A1AF radial-gradient(#FFFFFF, #FAFAFA);
   background-repeat: no-repeat;
   padding: 0;
+  display: flex;
+  flex-flow: column;
 }
 
 header {
@@ -46,6 +48,10 @@ header a {
   color: #078e3d;;
 }
 
+.main {
+  flex: 1;
+}
+
 footer {
   text-align: center;
   margin-top: 50px;
@@ -113,4 +119,4 @@ table tr:nth-child(even) td {
   .content {
     padding: 0 20px;
   }
-}
+}