.travis.yml: Tap Homebrew/core on Linux (#610)
.travis.yml: Tap Homebrew/core on Linux (#610)


hanxue/linuxbrew,Linuxbrew/brew,hanxue/linuxbrew,Linuxbrew/brew,maxim-belkin/brew,Linuxbrew/brew,maxim-belkin/brew,hanxue/linuxbrew,maxim-belkin/brew,Linuxbrew/brew