Require version 5.8.0.

Should fix test failure report on 5.6.2:
http://www.cpantesters.org/cpan/report/38ed848a-7062-11e2-9a79-ec413c106faf
DCANTRELL++
Correct documentation for all().

For: rt.cpan.org ticket #83169.  MRDVT@cpan.org++.