Move authors to the required attributes section

The authors setters were in the optional attributes section which is
incorrect.

Fixes rubygems/guides#76
Capture $VERBOSE early for ruby 1.8 and syck

I'm not sure how, but syck also disables warnings in a similar way and
this interfered with RubyGems enabling syck for tests.  This would cause
the contains_requirable_file? tests to fail on ruby 1.8 when ran after
with_syck.