[BioRuby] Xcode 5.1 and Biogems

[Joachim Baran]

Hello,

  I would update the biogems.info instructions myself, but I do not know
where I should do that.

  Mac OS X users with Xcode 5.1 and newer need to install 'bio-gem' like
this:

  sudo
ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future gem
install bio-gem

  That is related to command line options that are obsolete with the newest
clang.

Joachim