Refactor LocalDateTime#nextMatch logic

[kevincianfarini]

The current implementation is brittle and potential contains bugs like #26. We should try to find a reference cron test suite we can assert against.

[kevincianfarini]

This refactor should also take into account how to support multiple, non-contiguous values. For example:

5,10 0 10 * 1 

In cron this will run a task at 12:05 and 12:10 on every Monday as well as on the 10th of every month. The current representation of int ranges for the datetime matching forbids us from specifying 5,10.