Rename email rate limiting methods

[elliotthilaire]

trafficstars

This is a rename of skip_daily_email? method to emails_rate_limited?

When worked on this Job in the past I misunderstood why skip_daily_email? was skipping emails.

I thought it did more than skip because of the rate limiter. I introduced a bug (now been fixed) because of that misunderstanding. I think this rename makes it more clear.

[benoittgt]

With the commit from Nate it should be green

[schneems]

I rebased with master which had some changes to that file. Waiting for tests now.