feat: (BREAKING CHANGE) overhaul libp2p config and constructor

* docs: update chat example and add info to its readme
* docs: update echo example
* docs: update libp2p in browser example
* docs: update pubsub example
* docs: update peer and content routing examples
* docs: update discovery mechanisms example
* docs: update encrypted comms example
* docs: update protocol and stream muxing example
* feat: add config validation
* test: update CI configs, use only node 8

test/node.js

@@ -1,6 +1,5 @@
 'use strict'
 
-require('./base')
 require('./transports.node')
 require('./stream-muxing.node')
 require('./peer-discovery.node')
@@ -8,5 +7,5 @@ require('./pubsub.node')
 require('./peer-routing.node')
 require('./content-routing.node')
 require('./circuit-relay.node')
-require('./multiaddr-trim')
+require('./multiaddr-trim.node')
 require('./stats')