Add -n/--insert-final-newline option

[yassh]

for #81

[gajus]

That would be nice.

Now I am doing:

jsonlint --sort-keys --in-place --indent '  ' ./stylelintrc.json && echo "" >> ./stylelintrc.json

[michaelmior]

Would love to see this merged. I have some files I want to start automatically formatting but they have newlines at the end and I don't want to change that and while the workaround from @gajus is alright, an option would be much nicer.

[PeterDaveHello]

Hey @zaach, this patch could make jsonlint more powerful and helpful! Do you have a chance to take a review on it? Many thanks!