Fix cli comments parsing

[diegoreis42]

#711

I followed the patterns that sqlite has, so everything after -- is treated as a comment. A bunch of spaces and a -- is treated as a comment also.

[PThorpe92]

testing locally, I think we might have to handle cases like this too.

sqlite:

[diegoreis42]

testing locally, I think we might have to handle cases like this too.

sqlite:

I forgot to test this one, thanks! I'll work on that tonight. Do you think it needs an automated test?

EDIT: the fix was pretty trivial actually, just moved the check outside the self.input_buff.is_empty(), it should works fine now.