Allow comments in rules

[agroce]

Possible format:

line beginning with one space followed by two dashes followed by a space is a comment, e.g.,:

-- this rule is to remove synchronized to check tests handle concurrency

(shouldn't interfere with any real rules)

[agroce]

attn @sambacha

[sambacha]

attn @sambacha

Will test it, thanks

[agroce]

I don't know when exactly I'll get around to it -- may be a bit, due to various grant proposals in flight