[BioRuby] Changing the BioRuby license

[Pjotr Prins]

Separately, we want to align BioRuby's license with the new license
of Ruby:

  http://svn.ruby-lang.org/repos/ruby/tags/v1_9_3_0/NEWS

Ruby's License is changed from a dual license with GPLv2 to a dual
license with 2-clause BSDL.

Complicated, huh ;). Essentially it is a more free license: 'do with
the source what you want, as long as you maintain the copyright
notice, but don't blame us if something goes wrong'.

BioRuby's license is "The Ruby's License" without specifying versions,
therefore BioRuby's license will be updated to the new Ruby License.

Naohisa, Pjotr, Raoul, Francesco and Toshiaki