Replace std::endl by "\n" to avoid force flush

[bioinfornatics]

Dear,

we encounter on our cluster a huge loss of performance due to a flush on each line by the use of std::endl

This merge request help to reduce the impact of writing an output stream

[SoapZA]

@bioinfornatics your change is good, just switch to using the char literal '\n' instead of the string literal "\n" and I'll merge it.

[bioinfornatics]

Thanks @SoapZA