Allow completions to chain

[aphistic]

Right now if a method returns a type, the assigned variable can show completions but you're unable to chain them together.

Ex (as it is):
-- datastore.foo() returns a Foo, which has :bar
local test = datastore.foo()
test:bar() -- completion would show test:bar()

Ex (as it should be):
local test = datastore.foo():bar() -- would not show :bar() completion