Line-break long expectation failure messages

This makes failures somewhat easier to read. We still preserve whitespace
within lines to make whitespace-only failures readable, e.g.
expect('foo  bar').toEqual('foo bar'). See #296.

src/html/_HTMLReporter.scss

@@ -332,7 +332,7 @@ body {
 
     color: $text-color;
 
-    white-space: pre;
+    white-space: pre-wrap;
   }
 
   .jasmine-result-message span.jasmine-result {