Implemented the new leaderboard endpoint (there only is a weekly leaderboard), since the leaders endpoint (with range) didn't return the expected data. It did return friends only without ranking or other leaderboard data.
Renamed the weekly_leaderboard method to leaderboard, since there isn't another type of leaderboard.
Merge pull request #19 from kevintuhumury/master

Replaced the leaders endpoint with the actual leaderboard endpoint.
Change double-quotes to single-quotes

All non-interpolated strings changed to single-quoted
Copy edits and formatting
Merge pull request #21 from jcasimir/revising_readme

Copy edits and formatting
Add "activity_on_date_range" method.
Merge pull request #22 from anl/feature-activity-date-range

Add "activity_on_date_range" method.
Update README.md

Fix typo in README.
Merge pull request #23 from bnadlerjr/patch-1

Update README.md