As previously discussed, let's flip the switch ^^.

This exposes the problem that it will now be run
for everyone, even if one did not read the help
about the recommended repetition count.

This is not good. So i think we can do the smart thing:
```
$ ./compare.py benchmarks gbench/Inputs/test3_run{0,1}.json
Comparing gbench/Inputs/test3_run0.json to gbench/Inputs/test3_run1.json
Benchmark                   Time             CPU      Time Old      Time New       CPU Old       CPU New
--------------------------------------------------------------------------------------------------------
BM_One                   -0.1000         +0.1000            10             9           100           110
BM_Two                   +0.1111         -0.0111             9            10            90            89
BM_Two                   +0.2500         +0.1125             8            10            80            89
BM_Two_pvalue             0.2207          0.6831      U Test, Repetitions: 2. WARNING: Results unreliable! 9+ repetitions recommended.
BM_Two_stat              +0.0000         +0.0000             8             8            80            80
```
(old screenshot)
![image](https://user-images.githubusercontent.com/88600/41502182-ea25d872-71bc-11e8-9842-8aa049509b14.png)

Or, in the good case (noise omitted):
```
s$ ./compare.py benchmarks /tmp/run{0,1}.json
Comparing /tmp/run0.json to /tmp/run1.json
Benchmark                                            Time             CPU      Time Old      Time New       CPU Old       CPU New
---------------------------------------------------------------------------------------------------------------------------------
<99 more rows like this>
./_T012014.RW2/threads:8/real_time                +0.0160         +0.0596            46            47            10            10
./_T012014.RW2/threads:8/real_time_pvalue          0.0000          0.0000      U Test, Repetitions: 100
./_T012014.RW2/threads:8/real_time_mean           +0.0094         +0.0609            46            47            10            10
./_T012014.RW2/threads:8/real_time_median         +0.0104         +0.0613            46            46            10            10
./_T012014.RW2/threads:8/real_time_stddev         -0.1160         -0.1807             1             1             0             0
```
(old screenshot)
![image](https://user-images.githubusercontent.com/88600/41502185-fb8193f4-71bc-11e8-85fa-cbba83e39db4.png)