Refactor Manager#start

* extract the Runner starting into the Runner class
* extract waiting for the server start into the Server class
* also made the Manager.log accessible so that it can be pulled from
  Server
Update the initial UI open to use Launchy

This should make it work across platform, when previously it would
only work in OSX.
Add 'open' command to the CLI to open the web UI
Bump the version to rc2
Remove @show_notifications from unexpected exit

I incorrectly included checking this variable in the Manager where it
will never be set. The unexpected exit handler will now always attempt
notification.
Merge pull request #63 from acant/bug/exit_notification

Remove @show_notifications from unexpected exit
Merge pull request #64 from acant/feature/open_ui

Add CLI command to open the UI and convert to using launchy gem