This is now required by ffmpeg

This should increase a bit the compability with Excel files

This is a cosmetic patch only.

Signed-off-by: Antoine Tenart <antoine.tenart@ack.tf>

This commit takes care of removing residual metadata
added by mat2 during the cleaning of pdf.

Mypy doesn't like some annotation in web.py,
this commits aims at pleasing it.

Some terminals with a small number of column
could wrap the cli's output in a way that
would make the testsuite fail.
This commit break the tests in several smaller one
to mitigate this.

This issue was originally reported by eleius
[here](https://github.com/actionless/pikaur/issues/433), and forwarded as #153.

Mounting new, empty filesystem on /tmp makes impossible to use mat2 for manipulating files stored there. Especially it breaks running tests while creating package and using /tmp as temporary builddir which is common setup in Arch Linux:
https://aur.archlinux.org/packages/mat2/#comment-721221