Eric Freese 78e4379711 Fix moving cursor to end of buffer when suggestion accepted
$max_cursor_pos in this case was not the correct value to use. It was
calculated based on the old length of the $BUFFER. After the suggestion
is accepted, we need to recalculate the new max cursor length and use it
to set the $CURSOR.

Fixes issue . Follow-up to issue  (PR ).
..
buffer_max_size_spec.rb Lots of async changes
highlight_style_spec.rb Lots of async changes
original_widget_prefix_spec.rb Lots of async changes
strategy_spec.rb Add `after_sourcing` hook for tests
use_async_spec.rb Make asynchronous suggestions disabled by default
widget_lists_spec.rb Fix moving cursor to end of buffer when suggestion accepted