Mobile Responsive Styles (#580)

* WIP: Responsive styles

* Flip breakpoints, ensure doc doesn't spread

* Add MenuIcon

* Refactor Sidebar to share mobile responsive styles

* Fix accidental find/replace

* Tweak padding to take into account icon spacing

app/scenes/Settings/Members.js

@@ -41,7 +41,7 @@ class Members extends Component {
             {this.props.settings.members && (
               <MemberList column>
                 {this.props.settings.members.map(member => (
-                  <Member auto justify="space-between">
+                  <Member key={member.id} justify="space-between" auto>
                     <Flex>
                       <Avatar src={member.avatarUrl} />
                       <UserName>