Change default target resolution to HD 1920x1080.

If you aren't setting target width and height explicitly in the root div,
this change will likely affect the size and layout of your presentation
steps. See DOCUMENTATION.md for details and how to fix.

js/impress.js

@@ -169,9 +169,9 @@
 
     // Some default config values.
     var defaults = {
-        width: 1024,
-        height: 768,
-        maxScale: 1,
+        width: 1920,
+        height: 1080,
+        maxScale: 3,
         minScale: 0,
 
         perspective: 1000,