Filter the app_id in the VCR fixtures.

- Set the app_id to abcde (common across all tests).
- Add filter of sensitive data in spec_helper.
Update activity_data endpoint to use correct params.

- Do not pass the params hash to the get call in activity_data.
- Use new fixture based on update to activity_data endpoint call.
Add checks for required params and values in endpoints.

- Rename the activityId param to activityID.
- Remove the required params logic for aggregate_sports endpoint.
- Include in activity data and experience type endpoints.
- Add tests around new checks in endpoints spec.
Document the NikePlusGem code for YARD doctool.

- Add YARD gem to bundler dependency (Gemfile).
- Add task to generate documentation via YARD in rakefile.
- Document constructors, methods, and attributes in classes.