* increase node version 10.XX.1 => 14.15.0

* Remove node version from .travis

According to travis docs it isn't required when the project includes a
.nvmrc:
https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#specifying-nodejs-versions-using-nvmrc

* also add nvmrc to example

* try with direct install via nvmrc

* install node before yarn