`'` and `"` use a new function `triple_quotes_handle_trailing` which
handles trailing/existing quotes.
This handles expansion of`"|"`, where the second quote gets automatically
inserted by e.g. delimitMate.
UltiSnips snippets are taken from UltiSnips repo.
Putting them nearby the engine seems to be the wrong thing to do.
One reason is that there are two forks now.