[pgjdbc/pgjdbc] 1f8ac4: Update Contributing.md [skip ci]

Branch: refs/heads/master
  Home:   https://github.com/pgjdbc/pgjdbc
  Commit: 1f8ac4063b1fd04ccc05616e3533d68be9912333
      https://github.com/pgjdbc/pgjdbc/commit/1f8ac4063b1fd04ccc05616e3533d68be9912333
  Author: Dave Cramer <davecramer@gmail.com>
  Date:   2018-07-20 (Fri, 20 Jul 2018)

  Changed paths:
    M CONTRIBUTING.md

  Log Message:
  -----------
  Update Contributing.md [skip ci]

* Update Contributing.md

After reading this I realized it was a bit dated.
I've also attempted to massage the grammar.



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