be compatible with Scala 2.12 community build

[SethTisue]

NOTE: not to be merged as-is.

to keep including parboiled in the community build, we needed some
change like this because the community build now has ScalaTest 3.0.x,
not 2.x anymore.

in 3.0, scalactic is a separate dependency, and fail's signature
changed.

but I see you are using a variety of different ScalaTest versions,
depending on Scala version. perhaps you can move to ScalaTest 3.0
across the board...?

(if you don't want to mess with it, we could keep using my fork
in the community build...)

[sirthias]

Thanks, Seth!
I'm not sure whether it still makes sense to have this old version of parboiled in the community build. The parboiled-scala module is pretty much the oldest piece of Scala code I have written and it's quite unmaintained. Also, I don't think there are any real users left.

However, if you find it valuable to include sth like this in the community build, maybe to have some more coverage of "legacy Scala code", I wouldn't object, of course.

[SethTisue]

ok, how about this: could you make a community-build-2.12 branch in this repo with my changes (or give me rights to do so myself)? that way we can leave parboiled in a while longer (as long as it isn't giving us trouble) without having to point to my personal fork, which we try to avoid.

[sirthias]

@SethTisue of course, no problem. I'll happily give you full access rights.

[SethTisue]

thanks, I pushed up my branch