First character deleted from completion line on accept

[julienvincent]

As mentioned here: #20 (comment) there is an issue where the first character from the line being autocompleted is deleted when accepting an item:

(group-|)
;; Press <Cr> / your accept key
group-by|)

The first bracket is deleted. This does not occur, in this example, when adding a space at the beginning:

 (group-|)
;; Press <Cr> / your accept key
 (group-by|)

[julienvincent]

Maybe a more approachable reproduce guide:

In an empty lua file type:

{a|}

and accept the autocomplete item. Results in:

assert|}