use reopen instead of extend to re-open TopicController
add CurrentUser's email address to Zendesk ticket as collaborator

* so that both the user who creates the topic and the forum moderator that submits the Zendesk ticket get included on the ticket
confirm ticket exists before setting TopicController properties when finding Zendesk ticket
change generic addAlertButton to more specific addZendeskButton
refactor how the ticket json is rendered
add ability to log Zendesk API interactions
update zendesk-api client version
use ENV variables for Zendesk URLs
move Zendesk ticket #exists? method to base Zendesk class
refactor NewZendeskTicket class
update ticket status logic and css