MAINT: fixed bug in test
MAINT: fixed #504
REL: added note on bug fix
Merge pull request #505 from gregcaporaso/issue-504

annoying bug fix...
MAINT: relaxed requirement on sequences for distance computation, fixes #507
REL: noted in changelog
DOC: clarified comment
DOC: addressed bro's comment
DOC: addressed bro's comment
Merge pull request #508 from gregcaporaso/issue-507

relaxed requirements in BiologicalSequence.distance
Merge branch 'master' of git://github.com/biocore/scikit-bio into issue-225