base for future development

- the CT Ecto demo setup is much friendlier now, and it is also seeding the new database with demo data
- the labels support functions now
- the paths returned will always have the depth, as the 3rd element (breaking chance)

add support for pretty printing trees

print_tree witl return a list with tuples, if ops[:raw] is true

bugfix; on conflict nothing, can return nothing and print tree will only print the immediate children (depth 1)

Introducing v1.0.0

This is a new version introducing breaking changes. Please continue to use 0.2.1 for production, until we hit 1.2 unless you know what you're doing =)
minor code cleanup

- added credo, and using it
- .tool-versions; Elixir/Erlang upgrade

update asdf for using erlang 22.2.1, and elixir 1.10.3-otp-22