chore(.travis.yml): fix lean path for generating js/completion.js
chore(.travis.yml): fix lean path for generating js/completion.js

leanprover/tutorial,leanprover/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,Hodapp87/cs6460_project,avigad/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,avigad/tutorial,avigad/tutorial,soonhokong/lean-tutorial,leanprover/tutorial