improved accessibility

I gave all the <img>s alt attributes, which makes reveal.js a lot more accessible

index.html

@@ -66,7 +66,7 @@
 							try pressing <a href="#/2/1">down</a>.
 						</p>
 						<a href="#/2/1" class="image">
-							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png">
+							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" alt="Down arrow">
 						</a>
 					</section>
 					<section>
@@ -77,14 +77,14 @@
 						<h2>Basement Level 2</h2>
 						<p>Cornify</p>
 						<a class="test" href="http://cornify.com">
-							<img width="280" height="326" src="https://s3.amazonaws.com/hakim-static/reveal-js/cornify.gif">
+							<img width="280" height="326" src="https://s3.amazonaws.com/hakim-static/reveal-js/cornify.gif" alt="Unicorn">
 						</a>
 					</section>
 					<section>
 						<h2>Basement Level 3</h2>
 						<p>That's it, time to go back up.</p>
 						<a href="#/2" class="image">
-							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" style="-webkit-transform: rotate(180deg);">
+							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" alt="Up arrow" style="-webkit-transform: rotate(180deg);">
 						</a>
 					</section>
 				</section>
@@ -158,19 +158,19 @@
 							apply broader style changes, like switching the background.
 						</p>
 						<a href="#/7/1" class="image">
-							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png">
+							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" alt="Down arrow">
 						</a>
 					</section>
 					<section data-state="blackout">
 						<h2>"blackout"</h2>
 						<a href="#/7/2" class="image">
-							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png">
+							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" alt="Down arrow">
 						</a>
 					</section>
 					<section data-state="soothe">
 						<h2>"soothe"</h2>
 						<a href="#/7/0" class="image">
-							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" style="-webkit-transform: rotate(180deg);">
+							<img width="178" height="238" src="https://s3.amazonaws.com/hakim-static/reveal-js/arrow.png" alt="Up arrow" style="-webkit-transform: rotate(180deg);">
 						</a>
 					</section>
 				</section>
@@ -241,7 +241,7 @@ function linkify( selector ) {
 				<section>
 					<h2>Spectacular image!</h2>
 					<a class="image" href="http://hakim.se/experiments/html5/breakdom/" target="_blank">
-						<img width="320" height="412" src="https://s3.amazonaws.com/hakim-static/reveal-js/breakdom.png">
+						<img width="320" height="412" src="https://s3.amazonaws.com/hakim-static/reveal-js/breakdom.png" alt="BreakDOM game screenshot">
 					</a>
 				</section>