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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