CI setup

# Do not merge yet

This is work in progress and meant as base for discussion

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The idea is to make tests run in both, Node.js and browser, and to create a CI setup with Travis and Sauce Labs. I'd suggest to follow the lead of the PouchDB Team, they use npm tasks for all the things: https://github.com/pouchdb/pouchdb

- [x] `npm start` starts a dev server. Run tests at http://localhost:9000/tests/
- [x] `npm test-node` runs tests in Node.  
- [x] `npm test-browser` runs tests in Browser with Sauce Labs
- [x] Travis / CI with `npm test-browser`