Update evaluation.py MRR metrics as previous metrics is Wrong

[Yazooliu]

I updated the MRR metrics in evaluation.py and this PR update is related to issue: 119

please check and send me reponse, thanks

Yazooliu BR

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Yazooliu]

please check and approve.

[Yazooliu]

seems nobody maintenance for this ? @CLAassistant @ @nomagick @ZeyuChen @llxxxll please correct me if i mentioned the wrong person. thanks.