Return back LTreeField support
I wasn't interested in supporting it. 1.0 was also released back in 2012, a relative eternity ago.
I saw in 1.0.0 version peewee have LTreeField support, but now we have only HSTORE and JSON.
Why this feature dropped?

Previous inital support of ltree extension for PG
https://github.com/coleifer/peewee/commit/9959cd8142ecece6704fd82e9c6274de2794d8c4