Use rubygem(foo) or rubygem-foo

[Achilleas Pipinellis]

I know that both result to the same thing (if I remember correctly I had
asked Vit about this in IRC), but I have forgotten their real difference.

My attention got caught by a comment Josef made in one of his reviews
[0], saying that rubygem-foo is the new syntax. If that's the case, I
would like to propose 2 changes:

a) A reference in the wiki
b) An implementation for gem2rpm

I guess b) could be fairly easy by changing the templates.

By starting with these steps, there will be a push to use the new syntax
from now on. What do you think?

[0]: https://bugzilla.redhat.com/show_bug.cgi?id=979749#c2