Refactor Avatar and AvatarOverlay to have 'account' as prop instead of src and staticSrc (#4526)

* Refactored Avatar and AvatarOverlay (DRY) to have 'account' as prop.
Also removed animate attribute from compose navigation bar, which should
have never been there. Added test for avatar overlay.

* fix broken tests

* god dammit another bug in tests! travis please let this pass

* formatting in avatar overlay

app/javascript/mastodon/features/compose/components/navigation_bar.js

@@ -19,7 +19,7 @@ export default class NavigationBar extends ImmutablePureComponent {
       <div className='navigation-bar'>
         <Permalink href={this.props.account.get('url')} to={`/accounts/${this.props.account.get('id')}`}>
           <span style={{ display: 'none' }}>{this.props.account.get('acct')}</span>
-          <Avatar src={this.props.account.get('avatar')} animate size={40} />
+          <Avatar account={this.props.account} size={40} />
         </Permalink>
 
         <div className='navigation-bar__profile'>