Replace cmath::sqrt with std::sqrt

[grig-guz]

Fixed the previous pull request

[vigsterkr]

looks better... let's see what the CI says

[vigsterkr]

@grig-guz great! there are still some formatting errors. you can fix those by using clang-format; for details check the 8th point in https://github.com/shogun-toolbox/shogun/blob/develop/doc/readme/DEVELOPING.md

[grig-guz]

@vigsterkr thanks! However, I'm not sure how to fix some of these errors. I ran the clang-format-3.8 as recommended by the script, but I still get errors like these

[vigsterkr]

@grig-guz i'm not so sure what you mean by the cropped image but this is clearly a formatting problem:
https://travis-ci.org/shogun-toolbox/shogun/jobs/359204608#L760

or

result=1.0-CStatistics::normal_cdf(statistic, std_dev);

should be
result = 1.0 - CStatistics::normal_cdf(statistic, std_dev);

[grig-guz]

The style check passed. Is it fine now?
The problem was that the automatic reformatting tool was not fixing all errors. It was not doing anything in case when line padding was wrong (say, 8 spaces instead of 2 tabs), but the formatting error detection script was treating it as an error.

[grig-guz]

Also, the formatting error detection script was inconsistent in some places. Sometimes, it required for line padding to only consist of tabs, and in other classes it was asking for tabs and 2-3 spaces.

[karlnapf]

Thx for the patch!