Disable low battery CSS animation

Fixes #519.

src/sass/components/_battery.scss

@@ -3,8 +3,8 @@
     top: -18px;
     right: 24px;
 
-    &.alert {
-        animation: alert 1990ms linear infinite;
+    &.alert md-icon {
+        color: $status-error;
     }
 
     md-icon {
@@ -29,8 +29,4 @@
         top: 20px;
         left: 1px;
     }
-
-    @keyframes alert {
-        50% { opacity: 0.2; }
-    }
 }