WIP: xmpfilter stuff

Don't want to stash b/c I just lose everything I stash, but this is not working and is only half thought out
Fix bug where only last line of singleton method gets wrapped
Fix wrapping issue for singletons methods
Stick marker regexes into parse_args
InterpretFlags turns markers into regexes

Not directly tested, b/c I'm planning to yank the whole thing
into some marker object or something, so just let high-level tests
show that it works
Move annotation removal entirely into RemoveAnnotations
Some refactoring in RemoveAnnotation
Renamings in RemoveAnnotations
Some refactoring (and defactoring) in RemoveAnnotations
Show that xmpfilter updates "#=>" lines also

https://github.com/JoshCheek/seeing_is_believing/issues/44#issuecomment-57025827
RewriteComments can be given line numbers to inject
Xmpfilter annotator handles errors better