Tolerance not being used for task reordering

Currently, tasks are being sorted by start time only:
https://github.com/ARMmbed/minar/blob/master/source/minar.cpp#L336-L345

And the tolerance is only being used to evaluate if the top task can be executed:
https://github.com/ARMmbed/minar/blob/master/source/minar.cpp#L371

Proposal: the comparison function should take tolerance into account when sorting so that tasks with low tolerance values can skip ahead of tasks with high tolerances.

Read source/minar.cpp around lines 336-345 to understand the current start-time comparison, then inspect line 371 where tolerance is evaluated for the top task. Done means the sorting comparison accounts for tolerance so a low-tolerance task can move ahead of a high-tolerance task; the issue does not name a test to run.

Written by the indexing model from the issue text.