add title and alt for avatars, fix console errors in avatarlist

src/components/user_avatar/user_avatar.js

@@ -2,7 +2,7 @@ import StillImage from '../still-image/still-image.vue'
 
 const UserAvatar = {
   props: [
-    'src',
+    'user',
     'betterShadow',
     'compact'
   ],

src/components/user_avatar/user_avatar.vue

@@ -1,8 +1,10 @@
 <template>
   <StillImage
     class="avatar"
+    :alt="user.screen_name"
+    :title="user.screen_name"
+    :src="user.profile_image_url_original"
     :class="{ 'avatar-compact': compact, 'better-shadow': betterShadow }"
-    :src="imgSrc"
     :imageLoadError="imageLoadError"
   />
 </template>