implemented flex-nav

client/lib/sideNav.coffee

client/stylesheets/base.less

client/stylesheets/utils/_preloader.import.less

client/views/app/chatWindowDashboard.html

client/views/app/sideNav/channels.coffee

client/views/app/sideNav/channels.html

client/views/app/sideNav/channelsFlex.coffee

client/views/app/sideNav/channelsFlex.html

client/views/app/sideNav/chatRoomItem.coffee

client/views/app/sideNav/chatRoomItem.html

client/views/app/sideNav/directMessages.coffee

client/views/app/sideNav/directMessages.html

client/views/app/sideNav/privateGroups.coffee

client/views/app/sideNav/privateGroups.html

client/views/app/sideNav/privateGroupsFlex.coffee

client/views/app/sideNav/privateGroupsFlex.html

client/views/app/sideNav/sideNav.coffee

client/views/app/sideNav/sideNav.html

client/views/app/sideNav/starredRooms.coffee

client/views/app/sideNav/starredRooms.html