update .travis.yml * use container-based infrastructure * test on Node 0.12 and io.js
update .travis.yml
* use container-based infrastructure
* test on Node 0.12 and io.js

KCypher13/gulp-sourcemaps,jbenet/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps,opiants/gulp-sourcemaps,realtymaps/gulp-sourcemaps,phizaz/gulp-sourcemaps,honger05/gulp-sourcemaps,IveWong/gulp-sourcemaps,floridoo/gulp-sourcemaps,realtymaps/gulp-sourcemaps,realtymaps/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps,floridoo/gulp-sourcemaps,floridoo/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps