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
Remove @show_notifications from unexpected exit

I incorrectly include this variable into the manager, where it will
never be set. I have now changed the unexpected error handler to always
attempt notification.
Bump the version to rc2