Replace broken croniter

[urm8]

regarding this issues: #250, #260, for some reason,
for cronstring: 5 * * * * *
for local time: x:5:*, x in [0-24]
croniter yields x.5.01

@selwin do you actively maintain this repo ?

[selwin]

@urm8 thanks for the PR. Unfortunately not much work is going into this repo as RQ already has a built in scheduler (though not as fully featured as this repo because there are somethings that don't fit within the paradigm).

I'm happy to make releases every now and then to fix bugs though.