Remove node 8 engine restriction (#39)

* Update package.json to allow usage by modern node

Change the node engines to remove the upper limit

* Update mock-fs dependency

Prior to 4.8.0 there was an issue with mock-fs' implementation of
existsSync throwing an exception under node 10+ instead of returning
false when a mocked file didn't exist. See tschaub/mock-fs#256

* Add node 14 to the travis config

.travis.yml

@@ -2,5 +2,6 @@ language: node_js
 node_js:
   - "6"
   - "8"
+  - "14"
 after_success:
   - "yarn run coveralls"

package.json

@@ -15,7 +15,7 @@
 		"precommit": "lint-staged"
 	},
 	"engines": {
-		"node": ">=6.0.0 <9.0.0"
+		"node": ">=6.0.0"
 	},
 	"nyc": {
 		"exclude": ["**/*.spec.js"]
@@ -33,7 +33,7 @@
 		"lint-staged": "4.3.0",
 		"mocha": "3.2.0",
 		"mocha-lcov-reporter": "1.2.0",
-		"mock-fs": "4.4.2",
+		"mock-fs": "4.14.0",
 		"nock": "9.0.6",
 		"nyc": "10.1.2",
 		"prettier": "1.7.4",

yarn.lock

@@ -1852,9 +1852,10 @@ mocha@3.2.0:
     mkdirp "0.5.1"
     supports-color "3.1.2"
 
-mock-fs@4.4.2:
-  version "4.4.2"
-  resolved "https://registry.yarnpkg.com/mock-fs/-/mock-fs-4.4.2.tgz#09dec5313f97095a450be6aa2ad8ab6738d63d6b"
+mock-fs@4.14.0:
+  version "4.14.0"
+  resolved "https://registry.yarnpkg.com/mock-fs/-/mock-fs-4.14.0.tgz#ce5124d2c601421255985e6e94da80a7357b1b18"
+  integrity sha512-qYvlv/exQ4+svI3UOvPUpLDF0OMX5euvUH0Ny4N5QyRyhNdgAgUrVH3iUINSzEPLvx0kbo/Bp28GJKIqvE7URw==
 
 ms@0.7.1:
   version "0.7.1"