allow scheduler to schedule all pending tasks

[thatmattbone]

Switched the return to a continue so that any pending, run-once tasks can be sent to the broker in one shot.

This is particularly handy if there's a large amount of run-once tasks that are scheduled in the past and need to be caught up.

[codecov-io]

Current coverage is 90.82%

Merging #165 into master will decrease coverage by -5.80% as of b64fbcf

@@            master    #165   diff @@
======================================
  Files           40      40       
  Stmts         2724    2725     +1
  Branches         0       0       
  Methods          0       0       
======================================
- Hit           2632    2475   -157
  Partial          0       0       
- Missed          92     250   +158

Review entire Coverage Diff as of b64fbcf

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[Koed00]

Nice one