Remove bundler/jeweler dependency

[pjotrp]

Lately I have been writing gems without bundler/jeweler and simply using rake+gem. I don't know who is using biogem right now, but I think we can create a simpler tool - merely generating some output files from templates and use the rake command for pushing a gem to rubygems.

Do we want to do this?

[homonecloco]

I am still using it now and then, and I change jeweler `` to juwelier, but seems like the later is broken on ruby 2.6