Adding entities to allow modeling of a race

- model and specs for race
- model and specs for athlete
Adding form to create new race

Form takes a name for the race and numbers for each of the athletes
Adding cocoon gem to allow dynamic adding of athlete numbers

- re-organised gemfile to use groups and generally tidy it up
Working on create race should create race with athlete numbers

- Adding styling to add and remove buttons on athletes
can now create a race with any mumber of athletes
User can now view their races

- currently only showing a list of athlete numbers need to update this
  to call strava gateway and display the actual data
creating gateway class to fetch data from strava
Merge pull request #16 from the-race/create-race

Create race