[Front-end] [#178] Finished up the two-pane version for activity detail
[Front-end] [#178] Made 'Login to Join' button work, fixed up activities' call-to-action to align to the center
[Front-end] [#178] Fixed up not hiding some of the details
[Front-end] [#178] Enabled the disabling and rerouting to login for comment box (if user isn't logged in) & added a section for friends going
[Front-end] [#178] Added the number of people going as well & hide list if empty