Removed duplicated output on test failure.
Removed duplicated output on test failure.

See previous commits for further explanation.

In this case, here's a typical test output from before the change:

-------------------------------------------------------------------------------
------ Test started: Assembly: ConwaysGameOfLife04.dll ------

Test 'Ploeh.Katas.GameOfLifeProperties.Any live cell with < 2 live neighbors dies' failed: FsCheck.Xunit.PropertyFailedException :
Falsifiable, after 1 test (0 shrinks) (StdGen (825010647,296065548)):
Original:
(0, 0)

Output from Ploeh.Katas.GameOfLifeProperties.Any live cell with < 2 live neighbors dies:
  Falsifiable, after 1 test (0 shrinks) (StdGen (825010647,296065548)):
    Original:
    (0, 0)

0 passed, 1 failed, 0 skipped, took 0,93 seconds (xUnit.net 2.1.0 build 3179).
-------------------------------------------------------------------------------

Once again, notice the duplication of message between exception message
and output.

Here's the same test failure after removal of duplication:

-------------------------------------------------------------------------------
------ Test started: Assembly: ConwaysGameOfLife04.dll ------

Test 'Ploeh.Katas.GameOfLifeProperties.Any live cell with < 2 live neighbors dies' failed: FsCheck.Xunit.PropertyFailedException :
Falsifiable, after 1 test (0 shrinks) (StdGen (2130682669,296065549)):
Original:
(0, 0)

0 passed, 1 failed, 0 skipped, took 0,95 seconds (xUnit.net 2.1.0 build 3179).
-------------------------------------------------------------------------------

Duplication is gone.

fscheck/FsCheck,ErikSchierboom/FsCheck,fscheck/FsCheck,fsharp/FsCheck,ploeh/FsCheck,sideeffffect/FsCheck,jhamm/FsCheck