Update babel to 2.15.0#1126

pyup-bot wants to merge 1 commit intodevelopStuartJSquires/markov_slackbot:developfrom

pyup-update-babel-2.3.4-to-2.15.0StuartJSquires/markov_slackbot:pyup-update-babel-2.3.4-to-2.15.0Copy head branch name to clipboard