Bump version to 0.1.9
Avoid error due to change of library

Passing parameter like `Orgmode::Parser.new(document, 1)` is invalid.
Passing parameter like `Orgmode::Parser.new(document, offset: 1)` is valid.

See
https://github.com/bdewey/org-ruby/commit/3fb69867c5f829efb4839fd207865ff9e53e5ce5
Fix library dependencies