Update initial setup

* Add lines describing links to be created if using xmonad as the window
  manager

* Add separate section describing links to be created for using the
  compose key and defining custom key-mappings
Update plugins managed by Vundle

* Add supertab plugin

* Add D syntax highlighting plugin

* Remove ctab plugin until its need is felt
Merge pull request #1 from gautam-kotian-sociomantic/master

Initial setup + plugins changes