fix: Handle comments by stripping

[nikolaik]

This is an attempt at solving failed validation of commit texts with trailing comment lines which are usually added when writing the commit message in an editor, f.ex:

EDITOR=vim git commit -a

which on some systems gives you a templated commit message similar to this:

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch nikolaik/editor-comments
# Your branch is up to date with 'origin/nikolaik/editor-comments'.
#
# Changes to be committed:
#   new file:   yolo

Reported in #80

[thekaveman]

Thanks @nikolaik!

I added one extra check to your tests to ensure the actual commit message is unaltered. Otherwise this is great 👍