Use a pckage repository to install inkscape 1.0 on CI.

.travis.yml

@@ -12,6 +12,6 @@ addons:
     - ubuntu-toolchain-r-test
     packages:
     - g++-4.8
-before_install: "sudo apt-get update && sudo apt-get install -y libcairo2-dev libjpeg8-dev libgif-dev optipng pngcrush pngquant libpango1.0-dev graphicsmagick libjpeg-turbo-progs inkscape gifsicle"
+before_install: "sudo add-apt-repository -y ppa:inkscape.dev/stable && sudo apt-get install -y libcairo2-dev libjpeg8-dev libgif-dev optipng pngcrush pngquant libpango1.0-dev graphicsmagick libjpeg-turbo-progs inkscape gifsicle"
 script: "npm run-script travis"
 after_success: '<coverage/lcov.info ./node_modules/coveralls/bin/coveralls.js'