RFC: added draft for Competition model

[pieteradejong]

"Request for comment"
added to my fork -> feature branch 'pieter'
fields: startDate, endDate, criterium, groups, ranking, prize

link:
https://github.com/pieteradejong/fittr/blob/pieter/app/coffee/models/competition.coffee

[pieteradejong]

This model is designed to be a competition between two or more groups.
However, it might also be interesting to allow a user to challenge another user, on an individual basis. E.g. if they're both really into running. Perhaps those are sufficiently different things that they merit separate data models?

[Hendrixer]

I like it, i agree with the P 2 P competition feature, but this will work for now