adding flexbox fallback for grid--two class

opentech/static_src/src/sass/components/_grid.scss

@@ -15,6 +15,12 @@
         }
     }
 
+    &--two {
+        > * {
+            flex-basis: calc(50% - 20px);
+        }
+    }
+
     &--narrow {
         text-align: center;