Force name delimiter to be single hyphen.

The CPAN indexer may be confused if the base name (it is used in Build.PL as "name") uses double hyphens as name space delimiter (e.g. Foo--Bar).

Yes, I know we should not use double hyphens as delimiters, but GitHub converts double colons to double hyphens when we create a new repository, like so;
http://gyazo.com/0e1b40244556e14481c6bcadc310a5bb

So I fixed it.