Fix the stddev/mean computations which had be garbled since commit e5f5a0d30e91d94b0563a0c92bbc2a71b4361daa, leading to a mean that was not in the min/max range and to zero-divide in the stddev computation, among others.
Ignore the CPU time consumed when timing is paused.

Conflicts:
	src/benchmark.cc
Adding myself to the contributors
Adding myself to the contributors
Two bug fixes in KeepRunning.
Merge pull request #27 from pleroy/TwoBugs

Two bug fixes in KeepRunning
Print mean/stddev of the # of iterations.
Merge branch 'TwoBugs' into StatsPure
Less of a hack: avoid the division/multiplication if the stddev is 0.
Comment.
Merge pull request #25 from pleroy/StatsPure

Fix the stddev/mean computations
Merge branch 'GoogleMaster' into PausePure

Conflicts:
	src/benchmark.cc
Merge pull request #28 from pleroy/PausePure

Take the CPU time into account in PauseTiming/ResumeTiming
Fix a bug in the destruction of BenchmarkFamilies.
Merge pull request #31 from pleroy/DestructionPure

Fix a bug in the destruction of BenchmarkFamilies.