TST: disable linkcheck in Py3 (bug in Sphinx)
TST: disable linkcheck in Py3 (bug in Sphinx)

https://bitbucket.org/birkenfeld/sphinx/issue/1457/linkcheck-anchors-and-py3-cant-convert
jensreeder/scikit-bio,xguse/scikit-bio,anderspitman/scikit-bio,anderspitman/scikit-bio,SamStudio8/scikit-bio,corburn/scikit-bio,jairideout/scikit-bio,corburn/scikit-bio,jairideout/scikit-bio,johnchase/scikit-bio,Kleptobismol/scikit-bio,colinbrislawn/scikit-bio,jdrudolph/scikit-bio,Achuth17/scikit-bio,gregcaporaso/scikit-bio,demis001/scikit-bio,wdwvt1/scikit-bio,averagehat/scikit-bio,gregcaporaso/scikit-bio,Kleptobismol/scikit-bio,kdmurray91/scikit-bio,kdmurray91/scikit-bio,johnchase/scikit-bio,jensreeder/scikit-bio,wdwvt1/scikit-bio,demis001/scikit-bio,averagehat/scikit-bio,Achuth17/scikit-bio,xguse/scikit-bio,SamStudio8/scikit-bio,colinbrislawn/scikit-bio,Kleptobismol/scikit-bio,jdrudolph/scikit-bio