Lack of clarity around MaxConcurrency in README

[dan-pulley]

The readme specifies "a new job will not be scheduled if we are at or over a job's MaxConcurrency limit."

https://github.com/gocraft/work#job-concurrency

However the code implies the job will still be inserted, it just won't be selected or run.

work/redis.go

Line 107 in 5959e69

var redisLuaFetchJob = fmt.Sprintf(`

It appears that this is just an easily misread bit of text - I was concerned from the readme that the job would just fail to be created, but the code strongly seems to indicate that the job simply won't get worked on if we are over the concurrency limit.