util: shorten outdated grace period

[tychoish]

While working up #55, I realized that our problems might (largely) be
explainable by having a much longer than expected grace period. While
#55 might be a reasonable or useful change, it seems like running with
a tighter tollerance might be useful.

I chose 10ms somewhat arbitrarily. I think +/- an order of magnitude
would be fair.

[codecov-commenter]

Codecov Report

Merging #56 (f04cb53) into master (4d78f5c) will increase coverage by 0.10%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   86.22%   86.32%   +0.10%     
==========================================
  Files           8        8              
  Lines         530      534       +4     
==========================================
+ Hits          457      461       +4     
  Misses         52       52              
  Partials       21       21              

Impacted Files	Coverage Δ
quartz/scheduler.go	92.81% <100.00%> (+0.16%)	⬆️
quartz/util.go	90.00% <100.00%> (ø)

[reugn]

I see the concern. What do you think about adding it to StdSchedulerOptions? Cron's minimum interval is one second, so we can set the default value to 100 milliseconds.

[tychoish]

I see the concern. What do you think about adding it to StdSchedulerOptions? Cron's minimum interval is one second, so we can set the default value to 100 milliseconds.

Done!

[tychoish]

I've given this another pass, and I think the documentation and test cases are in better shape now.

Please tell me what you think!