Mapper

Updates to how URLs are built, updates to method params.

- [x] The methods now take an optional sport and league param before the options hash.
- [x] The URLs are now built with uri_template
- [x] If a league is passed, but not a sport, the league will (attempt to) be mapped to a sport.

I will create these issues to validate:

- [ ] Some of the methods need to be verified against the results. The ESPN API Docs do not have valid sample result objects for each method, so I will need to validate by using their docs. 
- [ ] Make sure all calls are correct and use the correct URL patterns for all cases.
- [ ] The specs are all valid, but could use some cleaning up.