Add task type as argument to builder

[rouzwawi]

In order to support encoding/decoding of task values from TaskContext, the Class of the task type needs to be stored with the task.

[codecov-io]

Current coverage is 92.50%

Merging #11 into master will increase coverage by +0.02% as of 62221c0

@@            master    #11   diff @@
=====================================
  Files           10     10       
  Stmts          346    347     +1
  Branches        13     13       
  Methods                         
=====================================
+ Hit            320    321     +1
  Partial          3      3       
  Missed          23     23       

Review entire Coverage Diff as of 62221c0

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