Updated .travis.yml to use Node v10
Updated .travis.yml to use Node v10

no issue

- see https://github.com/TryGhost/Ghost/commit/99c3338ca9fb5f0b42ea077b56861bb303e533ba#diff-354f30a63fb0907d4ad57269548329e3
- see https://docs.ghost.org/faq/node-versions/

matitalatina/Casper,alvareztech/Casper,Inchdev/blog-theme,Inchdev/blog-theme,russmckendrick/Casper,dlecina/StayPuft,dlew/Casper,jedidja/Casper,eduardochiaro/Casper-Light,matitalatina/Casper,dlecina/StayPuft,eduardochiaro/Casper-Light,jedidja/Casper,alvareztech/Casper,TryGhost/Casper,ImKcat/ImKcatCasper