Retrieves competitors for a single event by ID.

{
 "competitors": 
 [
 {
 "id": "1",
 "name": "Springer Dinger",
 "age": "3",
 "drawNumber": "4",
 "jockeyName": "Atzeni, A",
 "weightPounds": "134",
 "silkImageUrl": "http://whdn.williamhill.com/content/sportsbook/silks/55336.gif",
 "trainerName": "Varian, R",
 "ownerName": "Sheikh Mohammed Obaid Al Maktoum"
 "colour": "grey",
 "sex": "Male",
 "formGuide": "4-2711",
 "rating": "27",
 "overview":
 {
 "runner":"Good pedigree; took him five times to click but won his Lingfield novice nicely in the end and duly confirmed himself progressive by following up at Newmarket, again over 7f (good ground); pace was true there so form looks okay and rates a danger to all off 6lb higher."
 "sire":"top-class 2yo over 6-7f inc Phoenix S. Lagardere; sire of Group winners; good record with fillies",
 }
 ]
}