use duo-test
remove some deps
make: remove redundant targets
make test-browser: remove default arg
tests: add mocha.css
Merge pull request #331 from segmentio/add/duo-test

Add/duo test
Specify a node version in package.json
Require >= 0.11 node
Merge pull request #337 from nickhammond/node_11

Specify a node engine version
Update Readme.md