Use new API for atom.config.get

:warning: Depends on atom/atom@a1b4820c044073d2e46d0e2505ae7a1ee7e89272 being released in v0.166 :warning:
We usually only do this when there are already parentheses from a method call, or when the object is multi-line, as is common in [cson files](https://github.com/atom/autocomplete/blob/master/keymaps/autocomplete.cson)