Show seed at start of suite run

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

`have_attributes`/`an_object_having_attributes` is a new RSpec 3.1 feature, so I'm not surprised we have old specs that could benefit from it.  They don't need to be updated, and definitely do not change them as part of your main commit(s), but if you want to change them in a separate commit (or even a separate PR) that would be great.