Correctly set max_sets, max_workouts in the query string

max_sets & max_workouts filters were incorrectly set in the query
string, resulting in truncated query results.  Usually this resulted
in only getting the most recent 31 activities from Fitocracy.

More details in https://github.com/sjoconnor/fitocracy-api/issues/5
Merge pull request #1 from nurpax/max_sets_fix

Correctly set max_sets, max_workouts in the query string