Mean bias

[henriquelettieri]

The first pull request to implement the halo bias in master

[coveralls]

Coverage: 49.032% (+3.03%) from 46.0% when pulling b9acf57 on mean_bias into 392bd34 on master.

[vitenti]

Add a minimal documentation and unit tests to halo bias objects.

[vitenti]

@henriquelettieri and @eduardojsbarroso this pull request is just waiting for you to add minimal documentation and unit tests to halo bias objects.

[eduardojsbarroso]

Ok, I just don't know if I can do it this week

[eduardojsbarroso]

@henriquelettieri and @eduardojsbarroso this pull request is just waiting for you to add minimal documentation and unit tests to halo bias objects.

I didn't find a good reference for the bias in nc_halo_bias_st_ellip.c object. I can deduce the bias function from the code but I do not know what the new parameters mean to write on the documentation. Do you guys have a reference for this equation?