Vim - Fix autocomplete

[agarrharr]

Figure out why javascript autocomplete sometimes knows built-in js functions and sometimes it doesn't. For example, open a JavaScript file and type [].. Sometimes, this will show a list of methods on Array.Prototype with their descriptions in the Quickfix window, and sometimes it doesn't. I think it has something to do with the presence of a .tern-port or .tern-project file.