add output aware interface and have process helper implement it
finish fixing this part of the tests
Merge pull request #6 from cordoval/6-make-process-helper-implement-output-aware-interface

This PR was merged into gushphp:master branch.

Discussion
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Make process helper implement output aware interface

as @dantleech proposed the input aware interface there is the analogous for the output

imported from https://github.com/cordoval/gush/issues/222

Commits
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489d0b7f4bb37471eba024f389caed47ac5c8f53 add output aware interface and have process helper implement it cordoval
fe39e1b866688cb4a7a9d6e8491cdd1cccf425a6 finish fixing this part of the tests cordoval