feat(issue-4): make error reporting more user friendly

[albx79]

Closes #4

Intercept error Results and log them properly, in red, printing only
the description.

This looks a lot better, to a final user, than the
json dump we used to have.

Example:

$ what bump HEAD^^^^^^^^^^^^^^^^^^^^ --strict
WARN - Commit 856bbbb068429221ca58083fe281bf40edbcd9b5 has more than one parent
WARN - Not a conventional commit message: "change license in Cargo"
WARN - Not a conventional commit message: "added CircleCI badge"
WARN - Not a conventional commit message: "added sample circle ci rust config"
WARN - Not a conventional commit message: "Merge branch 'master' of https://github.com/sky-uk/what-bump"
ERROR - Some non-conventional commit messages were encountered while running in `strict` mode

(and it's coloured, too!)