changed according the new support of Sequence for lowercase
changed according the new support of Sequence for lowercase

kdmurray91/scikit-bio,kdmurray91/scikit-bio,corburn/scikit-bio,gregcaporaso/scikit-bio,jairideout/scikit-bio,corburn/scikit-bio,anderspitman/scikit-bio,jairideout/scikit-bio,jdrudolph/scikit-bio,jdrudolph/scikit-bio,gregcaporaso/scikit-bio,anderspitman/scikit-bio