Fix star rating display

A TA with 4.9 rating has 4 stars displayed, whereas a TA with 4.7 rating had 4 stars and a half displayed. It would be better if it was displayed the following way:

x.0 - x.25: x stars
x.25 - x.75: x.5 stars
x.75 - x + 1: x+1 stars

see: