Update Brightray to latest master
Update Brightray to latest master

* vendor/brightray 2784337...487be20 (29):
  > Remember where the dev tools were docked between launches
  > Add preferences support for embedding applications
  > Strip whitespace from the application name in the user agent
  > Include the application's version number in the user agent string
  > Allow embedders to provide their own BrowserContext implementation
  > Implement Notification.close()
  > Make NotificationID more useful
  > Fire a `click` event when a notification is clicked
  > Don't fire the `show` event until the notification is actually shown
  > Add CreateUserNotification helper function
  > Show notifications even when the app is focused
  > Turn NotificationPresenter into an abstract base class
  > Move notification-related code into a new NotificationPresenter class
  > Fire a `show` event when a notification is shown
  > Add bare-bones HTML notifications support
  > Bump the base SDK and deployment target to 10.8
  > Allow embedders to customize the deployment target and base SDK
  > Allow overriding MainDelegate::BasicStartupComplete
  > Support undocking the devtools view into its own window
  > Support docking the devtools on the right side of the window
  > Make the devtools close button work
  > Merge InspectableWebContentsImpl and DevToolsFrontend
  > Fix double-delete of BrowserMainParts
  > Fix lifetime management of URLRequestContextGetter
  > Persist cookies to disk
  > Update libchromiumcontent
  > Update libchromiumcontent to pull in more headers
  > Update libchromiumcontent to pull in more headers
  > Allow overwriting vendor/download/libchromiumcontent when its version changes

atom/brightray_example,atom/brightray_example,atom/brightray_example