Refactor css to support theming

Move away from inline style attributes for setting contact colors.
Apply colors by name via css classes instead. Also lays groundwork
for syncing contact colors.

// FREEBIE

js/models/conversations.js

@@ -8,21 +8,21 @@
    // TODO: Factor out private and group subclasses of Conversation
 
    var COLORS = [
-        '#EF5350', // red
-        '#EC407A', // pink
-        '#AB47BC', // purple
-        '#7E57C2', // deep purple
-        '#5C6BC0', // indigo
-        '#2196F3', // blue
-        '#03A9F4', // light blue
-        '#00BCD4', // cyan
-        '#009688', // teal
-        '#4CAF50', // green
-        '#7CB342', // light green
-        '#FF9800', // orange
-        '#FF5722', // deep orange
-        '#FFB300', // amber
-        '#607D8B', // blue grey
+        'red',
+        'pink',
+        'purple',
+        'deep_purple',
+        'indigo',
+        'blue',
+        'light_blue',
+        'cyan',
+        'teal',
+        'green',
+        'light_green',
+        'orange',
+        'deep_orange',
+        'amber',
+        'blue_grey',
     ];
 
   Whisper.Conversation = Backbone.Model.extend({
@@ -360,10 +360,10 @@
             if (title) {
                 color = COLORS[Math.abs(this.hashCode()) % 15];
             } else {
-                color = '#999999';
+                color = 'grey';
             }
         } else {
-            color = '#2090ea';
+            color = 'default';
         }
 
         if (this.avatarUrl) {