Disable terminal colorization if `TERM=dumb` is set

[Urhengulas]

This PR fixes the problem @fhars described in #318:

The current version of the colored crate ignores the capabilities of the terminal (see https://github.com/mackwic/colored/issues/108), which makes the outupt of probe-run unparseable in e.g. emacs compilation mode.

It also supersedes #318 as a fix to the problem. The reason for not going with #318 is that it adds the terminfo crate as a dependency which seems unmaintained and with many outdated dependencies.

[jonas-schievink]

bors r+

[bors[bot]]

Build succeeded:

• ci