add a post-install msg to gemspec
add a post-install msg to gemspec

linneakirby/nea,acl2018/acl2018-website,mbibko/mbibko.github.io,plcarman/plcarman.github.io,jcclose1/jcclose1.github.io,acl2018/acl2018-website,tomerlichtash/maxima,oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo/oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo,saintsal/saintsal.github.io,dirkgomez/minima,mbibko/mbibko.github.io,plcarman/plcarman.github.io,oncleben31/minima,oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo/oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo,acl2018/acl2018-website,Cj-Malone/minima,tomerlichtash/maxima,linneakirby/minima,family-guy/minima,valimisliitkodu/valimisliitkodu.github.io,oncleben31/minima,alxn/minima,keluargacactus/beta,plcarman/plcarman.github.io,plcarman/plcarman.github.io,Cj-Malone/minima,jcclose1/jcclose1.github.io,Passw/Passw.github.io,chinaestone/chinaestone.github.io,Passw/Passw.github.io,mbibko/mbibko.github.io,oncleben31/minima,jekyll/minima,alxn/minima,yoon28/yoon28.github.io,jcclose1/jcclose1.github.io,keluargacactus/beta,jekyll/minima,saintsal/saintsal.github.io,dirkgomez/minima,linneakirby/nea,cgerke/cgerke.github.io,valimisliitkodu/valimisliitkodu.github.io,Cj-Malone/minima,yoon28/yoon28.github.io,thesixleave/thesixleave.github.io,chinaestone/chinaestone.github.io,dirkgomez/minima,alxn/minima,saintsal/saintsal.github.io,thesixleave/thesixleave.github.io,Passw/Passw.github.io,horaceho/horaceho.github.io,family-guy/minima,family-guy/minima,keluargacactus/beta,cgerke/cgerke.github.io,yoon28/yoon28.github.io,linneakirby/minima,valimisliitkodu/valimisliitkodu.github.io,thesixleave/thesixleave.github.io,keluargacactus/beta,horaceho/horaceho.github.io,cgerke/cgerke.github.io,saintsal/saintsal.github.io,tomerlichtash/maxima,oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo/oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo,horaceho/horaceho.github.io,jekyll/minima