Add option for rigorous in benchmark.conf.sample

[Fidget-Spinner]

Closes#445

No tests because there are no current tests for the option configurations in the current file :(.

I have manually verified that it works on my system.

[corona10]

lgtm!

The test failure does not looks like reated to this PR.
But need to check

pyperformance/pyperformance/tests/test_commands.py

Lines 147 to 167 in 0ffe825

	deftest_run_and_show(self):
	filename=self.resolve_tmp("bench.json")
	# -b all: check that *all* benchmark work
	#
	# --debug-single-value: benchmark results don't matter, we only
	# check that running benchmarks don't fail.
	# XXX Capture and check the output.
	self.run_pyperformance(
	"run",
	"-b",
	"all",
	"--debug-single-value",
	"-o",
	filename,
	capture=None,
	)
	# Display slowest benchmarks
	# XXX Capture and check the output.
	self.run_module("pyperf", "slowest", filename)