Show seed at start of suite run

Have the reporter notify formatters of the seed used on `start`
Attempt at tackling #1719 

Hmm, wouldn't that try to trigger a call to `start` on the formatter (which isn't defined)? Maybe I'm misunderstanding because I'm still trying to wrap my head around the FormatterSupport module. I was able to use this though: `send_notification :seed, seed_notification(10)`