closure notes displayed when re-open
added model link_type and its specs
replaced active with disabled, added disabled checkbox to link type edit
added link model, relationship, model specs
added links controller
code for adding links
added code for fetching ticket info with access token
for saving comments to tickets
listing links on edit/show page
track download of attachment
added deletion of link
replaced the info of ticket after matching access token and added a error class to error message
replaced double quotes with single
added ticket relationship with link, updated existing code and specs
added activity for create/delete link
added link relationship with activity model
added paper trail and added a scope for active link types
Specs added for track download of attachments
added more specs for link model
Cucumber specs added for tracking of downloading