compute total-significance by ratio paired t-test

Total-significance isn't good in current results, we should not use
standard paired t-test for it.

This patch use ratio paired t-test to compute total-significance,
just compute logarithm of samples and then execute standard paired
t-test.

Example: (we can see the p-value is reduced obviously, expected)
 control: [ 1  2  4  8 16]
 treated: [ 2  4  8 16 32]
 p-value: 0.0854412369731

 control: [ log(1)  log(2)  log(4)  log(8)  log(16)]
 treated: [ log(2)  log(4)  log(8)  log(16) log(32)]
 p-value: 8.88531529942e-65

Signed-off-by: Amos Kong <akong@redhat.com>
Merge pull request #940 from kongove/for-lmr

 compute total-significance by ratio paired t-test