title: Setting Label manually in Sentry
body: <p>I'm using Sentry for logging errors etc. It works fine when creating a SentryEvent with a supplied Exception object. I'm trying to create ones that do not come from an exception, just a condition that needs to be flagged up on the system. 
  To this extent I've set the exception to null and everything works fine, except that the issue has '' as its title. I can't find anywhere in the SentryEvent object that I can set as a title to avoid this. </p>
  
  <p>How do I label an event manually?</p>