added comment parameter (issue #3)

comments can be added by using the following format:

comment<delimiter><bugid> = text

where <delimiter> can be any character.

e.g.:
<mantis>
bugid = 4, 8, 13, 42
show = id, category, priority, created, updated, summary
comment.4 = This bug should be closed
comment/42 = Answer to the Ultimate Question of Life, The Universe, and Everything
comment#13 = Friday
</mantis>