Add more fixation detection methodS

[hatran22]

Hi @nalmadi, Ideally we want to provide users with more fixation detection methods. Other than the dispersion-based, we can, for example, use the 10 methods benchmarked in this paper https://link.springer.com/content/pdf/10.3758/s13428-016-0738-9.pdf. Also it would be useful if we can add more documents for this one.