Updating code for issue #1, the "fetch_more" method now loads more records from nike and append in existing activities.
Issue #3, Updated code for following changes,

1. person.rb - Passing 'count' to load records specified by user.
2. activities.rb - Passing query on the initial API call, to pass 'count' and load records specified by user.
issue #5,

Raising an exception if response contains invalid token error.
issue #7,

1. Added new method 'fetch_all' to fetch all activities.
2. Refactored the code, added new private method 'fetch_and_build_activities'