1. Ask all your users to uninstall the Chrome Extension "Groove".
2. If you added a site for email open tracking (not common), you will want to deactivate it.
a. In Salesforce from Setup, Click Develop | Sites.
b. In the row Groove click Edit.
c. In the field labeled Active Site Home Page, delete "GrooveTracker" so that the field is blank.
d. Deactivate the site by unchecking the field Active. Click Save
3. Un-assign all users from the permission set "Groove Standard Permissions":
a. From setup click Manage Users | Permission Sets
b. In the list of all permission sets click on Groove Standard Permissions
c. At the top click the button "Manage Assignments" - this takes you to a list of all users that are assigned to the Groove permission set
d. Select all users by clicking the check box in the top left corner
e. Click the button Remove Assignments - all users are now unassigned from the Groove permission set
4. Uninstall the managed package "Groove".