Updated ManualDispatchQueue to run items scheduled during a tick

[dsrees]

• Updated the ManualDispatchQueue to account for tasks that are scheduled within the tick time.
• Added tests for the ManualDispatchQueue to make sure if behaves as expected
• Updated channel tests that assumed the fake clock did not trigger work that was scheduled in the past
• Moved files around to be clean

[codecov-io]

Codecov Report

Merging #62 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #62 +/- ##
=========================================
Coverage 91.23% 91.23% Complexity 179 179 =========================================
Files 9 9 Lines 525 525 Branches 69 69 =========================================
Hits 479 479 Misses 14 14 Partials 32 32

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