user profile enhancements/changes

[ptitzler]

• Link to user's SO profile, e.g. http://stackoverflow.com/users/5244530/ptitzler (my suggestion would be to link to the activity summary tab http://stackoverflow.com/users/5244530/ptitzler?tab=topactivity because it provides the most useful information)
• Remove Slack ID from profile display (seems to serve no real purpose + cannot be changed)
• Add link to Slack team

[mmcelaney]

Get rid of Slack ID, keep Slack name and Stack Overflow ID. Add Slack Team. See comment below in regard to SO Profile link update.

[mmcelaney]

Update user's SO profile from http://stackoverflow.com/users/5244530/ptitzler to link to the activity summary tab http://stackoverflow.com/users/5244530/ptitzler?tab=topactivity because it provides the most useful information.

[mmcelaney]

@lornajane I want to remove this part from this task since it requires editing a separate part of the app that effects multiple pages. "Update user's SO profile from http://stackoverflow.com/users/5244530/ptitzler to link to the activity summary tab http://stackoverflow.com/users/5244530/ptitzler?tab=topactivity because it provides the most useful information."

[mmcelaney]

Made Task #92 to accommodate the SO Profile ask.