Check coverage with tarpaulin

Fix processing \newpage for Latex
(it finds that 'ewpage' is an error)

Try to optimize for performance

README: Add link to a nice asciinema demo (or a gif)

Filter mode (read stdin, write stdout)

Write more tests for kak.rs

Undo?

Project handling
  add a skyspell --project . option
  ignore list per project
  only check files belonging to the current project
  remember lang per project
