Some small fixes

Things we fixed

• Latest eslint-config-airbnb-base requires eslint4.*, but this template uses eslint 3.*, so the config is downgraded to a version compatible with eslint 3.*. We will soon upgrade to eslint 4.*, but have to run some tests first.
• fix a typo in config/index.js

Things we cleaned up

• Fix README explanation about devserver port 8080 to reflect port detection introduced in 1.1.0