Add handling of terminators to cursor_context

[josevalim]

Elixir and Erlang/OTP versions

All

Operating system

All

Current behavior

Currently we don't provide any specific completion suggestions after ) and friends.

Expected behavior

At the right side of ), ], }, >>, ', ", /, an atom or a number, we can only have a binary operator or one of the keywords (do, end, after, rescue, catch else), so we should emit a special instruction in order to provide better autocompletion.