Continuous hinting should not trigger completer on paste

[krassowski]

Follow up on #334.

Description

Paste incorrectly triggers completer (when the trigger character is present at the beginning of pasted text but followed with other text and not ending with the trigger character).

Starting with {}:

• paste . does not currently trigger, but we could support it (low priority)
• paste .keys() triggers but should not (bug, high priority)
• paste .keys(). does not currently trigger, but we could support it (low priority)

Reproduce

Expected behavior

Paste does not trigger completion if dot is the trigger character is not the last character.

Context

Master