Add the date for activity summary

[caiofelipe97]

Is your feature request related to a problem? Please describe.
I want to retrieve the activity summary for a given date range, but I don't know what data is related to which day.

Describe the solution you'd like
Update the getActivitySummary method to include the days we got data, even with 0, and/or attach the date to the activity summary response object.

Describe alternatives you've considered
Create a new method to get only the exercise minutes with a start and end date.