Fix modal layout

The styles in the upgraded react-modal broke our centering.
The auto-focusing on the modal made an annoying blue border around it in Chrome.

src/components/modal/modal.jsx

@@ -11,6 +11,7 @@ var defaultStyle = {
         backgroundColor: 'rgba(0, 0, 0, .75)'
     },
     content: {
+        position: 'absolute',
         overflow: 'visible',
         borderRadius: '6px',
         width: 500,

src/components/modal/modal.scss

@@ -1,6 +1,10 @@
 @import "../../colors";
 
 .ReactModal__Content {
+    &:focus {
+        outline: none;
+    }
+
     iframe {
         border: 0;
     }