opera-beta.rb: upgrade to v31.0.1889.98
opera-beta.rb: upgrade to v31.0.1889.98

chadcatlett/caskroom-homebrew-versions,pquentin/homebrew-versions,dictcp/homebrew-versions,tomschlick/homebrew-versions,lukaselmer/homebrew-versions,nicday/homebrew-versions,coeligena/homebrew-verscustomized,noamross/homebrew-versions,lukasbestle/homebrew-versions,elovelan/homebrew-versions