update deps and node versions (#9)

* update deps and node versions

* update dat-dns

Author: Joe Hand

.travis.yml

@@ -1,9 +1,8 @@
 language: node_js
 node_js:
-  - '4'
   - '6'
   - '8'
-  - '9'
+  - '10'
 cache:
   directories:
     - node_modules

README.md

@@ -12,7 +12,7 @@ resolve urls, links to a dat key using common methods
 * URLs with keys in them (`datproject.org/6161616161616161616161616161616161616161616161616161616161616161`)
 * `hyperdrive-key` or `dat-key` headers
 * Url to JSON http request that returns `{key: <dat-key>}`
-* Dat-DNS resolution ([details](https://github.com/beakerbrowser/beaker/wiki/Authenticated-Dat-URLs-and-HTTPS-to-Dat-Discovery))
+* Dat-DNS resolution (via [dat-dns](https://github.com/datprotocol/dat-dns))
 
 ## Install