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.

DOCUMENTATION.md

@@ -21,8 +21,12 @@ You need to use pixel values. The pixel values used here correspond to the `data
 given to the `#impress` root element. When the presentation is viewed on a larger or smaller screen, impress.js
 will automatically scale the steps to fit the screen.
 
-**NOTE:** I intend to change the defaults to target HD screens in 2021. So you may want to make a habit
-of explicitly defining these attributes for now, to avoid any disruption when the defaults change.
+**NOTE:** The default width and height have been changed to target HD screens in v1.2.0. If you
+don't set target width and height explicitly, layout and dimensions of your presentations are likely
+to be affected. In order to get back the old target resolution, use:
+
+    <div id="impress" data-width="1024" data-height="768" data-max-scale="1" data-min-scale="0"
+
 
 You can also control the perspective with `data-perspective="500"` giving it a number of pixels.
 It defaults to 1000. You can set it to 0 if you don't want any 3D effects.
@@ -36,9 +40,9 @@ See also [the plugin README](src/plugins/README.md) for documentation on `data-a
 Attribute                | Default   | Explanation
 -------------------------|-----------|------------
 data-transition-duration | 1000 (ms) | Speed of transition between steps.
-data-width               | 1024 (px) | Width of target screen size. When presentation is viewed on a larger or smaller screen, impress.js will scale all content automatically.
-data-height              | 768 (px)  | Height of target screen size.
-data-max-scale           | 1         | Maximum scale factor. (Note that the default 1 will not increase content size on larger screens!)
+data-width               | 1920 (px) | Width of target screen size. When presentation is viewed on a larger or smaller screen, impress.js will scale all content automatically.
+data-height              | 1080 (px) | Height of target screen size.
+data-max-scale           | 3         | Maximum scale factor. (Note that the default 1 will not increase content size on larger screens!)
 data-min-scale           | 0         | Minimum scale factor.
 data-perspective         | 1000      | Perspective for 3D rendering. See https://developer.mozilla.org/en/CSS/perspective
 

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,

src/impress.js

@@ -167,9 +167,9 @@
 
     // Some default config values.
     var defaults = {
-        width: 1024,
-        height: 768,
-        maxScale: 1,
+        width: 1920,
+        height: 1080,
+        maxScale: 3,
         minScale: 0,
 
         perspective: 1000,