fix(keymaps): Listen to atom commands instead of DOM events

Using `addEventListener` only works when the command is triggered by the atom keymaps manager, NOT when the command is triggered by the command registry (NylasEnv.commands.dispatch). Odds are, when you subscribe to key commands you /really/ mean to subscribe to the command, no matter how it's invoked.

This fixes #556, in which the down / up arrows in the message list weren't working.

internal_packages/thread-list/lib/thread-buttons.cjsx

@@ -150,6 +150,7 @@ DownButton = React.createClass
   _onClick: ->
     return if @state.disabled
     NylasEnv.commands.dispatch(document.body, 'core:next-item')
+    return
 
   _getStateFromStores: ->
     disabled: @isLastThread()
@@ -173,6 +174,7 @@ UpButton = React.createClass
   _onClick: ->
     return if @state.disabled
     NylasEnv.commands.dispatch(document.body, 'core:previous-item')
+    return
 
   _getStateFromStores: ->
     disabled: @isFirstThread()

src/components/key-commands-region.cjsx

@@ -113,22 +113,16 @@ class KeyCommandsRegion extends React.Component
   # particular scope, we simply need to listen at the root window level
   # here for all commands coming in.
   _setupListeners: (props) ->
-    _.each props.globalHandlers, (callback, handler) ->
-      window.addEventListener(handler, callback)
-
+    @_globalDisposable = NylasEnv.commands.add('body', props.globalHandlers)
     return unless @_mounted
     $el = React.findDOMNode(@)
-    _.each props.localHandlers, (callback, handler) ->
-      $el.addEventListener(handler, callback)
+    @_localDisposable = NylasEnv.commands.add($el, props.localHandlers)
 
   _unmountListeners: ->
-    _.each @props.globalHandlers, (callback, handler) ->
-      window.removeEventListener(handler, callback)
-
-    return unless @_mounted
-    $el = React.findDOMNode(@)
-    _.each @props.localHandlers, (callback, handler) ->
-      $el.removeEventListener(handler, callback)
+    @_globalDisposable?.dispose()
+    @_globalDisposable = null
+    @_localDisposable?.dispose()
+    @_localDisposable = null
 
   render: ->
     <div className="key-commands-region #{@props.className}">