fix half ratings

[alexkuz]

Currently half ratings are shown incorrectly for some currentRating values (e.g. 4.2 shows as 3 and a half stars). This fix implements this logic:

currentRating < 0.25 - shows empty star,
0.25 <= currentRating < 0.75 - shows half star,
0.75 <= currentRating - shows full star.

[amitthakkar22288]

although the half stars work now, the onChange does not send down the accurate value (2.5), instead it sends down 3.