Update Modernizr to remove Respond. Change placeholder Media Query.

Previous version of Respond was known to cause problems in IE8.
It was not necessary for developers who chose to write their CSS
in a 'mobile first' manner. Furthermore, there are some concerns
about the performance penalty Respond imposes upon legacy versions
of IE. If a future version of Respond is shown to be performant
and more reliable, it may be reconsidered for inclusion.

Along with this change is a simplification of the placeholder
Media Queries. Now there is only 1 Media Query example and it is
more clearly labelled as an example. The use of `em` units in the
condition is to reinforce the idea that Media Query breakpoints
should not be device-specific.

Fix #816

css/style.css

@@ -1,5 +1,5 @@
 /*
- * HTML5 ✰ Boilerplate
+ * HTML5 Boilerplate
  *
  * What follows is the result of much research on cross-browser styling.
  * Credit left inline and big thanks to Nicolas Gallagher, Jonathan Neal,
@@ -221,19 +221,13 @@ td { vertical-align: top; }
 
 
 /* ==|== media queries ======================================================
-   PLACEHOLDER Media Queries for Responsive Design.
-   These override the primary ('mobile first') styles
+   EXAMPLE Media Query for Responsive Design.
+   This example overrides the primary ('mobile first') styles
    Modify as content requires.
    ========================================================================== */
 
-@media only screen and (min-width: 480px) {
-  /* Style adjustments for viewports 480px and over go here */
-
-}
-
-@media only screen and (min-width: 768px) {
-  /* Style adjustments for viewports 768px and over go here */
-
+@media only screen and (min-width: 35em) {
+  /* Style adjustments for viewports that meet the condition */
 }