[hint addons] Don't include text after the cursor in completion

Completing inside a word used to try and take the whole word into
account. This is not typical completion behavior, and often not what
you want. After this change, the addons only take the part of the
word in front of the cursor into account.
[python-hint addon] Delete

The code was confused beyond belief, and the hintWords
functionality will provide the same completion power
without loading an additional addon.