Contrib/165

[PaulJackson123]

Simple fix that adds a heuristic to the maze example so that A* can take advantage of it.

My fist pull request so feedback on style is appreciated.

Thanks.

-Paul

[codecov-io]

Current coverage is 52.83%

Merging #166 into 1.0.X will not affect coverage as of bb97759

@@            1.0.X    #166   diff @@
=====================================
  Files          57      57       
  Stmts        1622    1622       
  Branches      264     264       
  Methods                         
=====================================
  Hit           857     857       
  Partial        63      63       
  Missed        702     702       

Review entire Coverage Diff as of bb97759

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[pablormier]

Congrats for your first pull request! everything looks fine.