refactor: updates dependencies to fix CVE-2015-8315 (#62)

BREAKING CHANGE: Enforces `engines` of `"node": ">= 8.9.0"`

BREAKING CHANGE: Updates to `source-map@^0.7.2` which requires NodeJS >= 8

BREAKING CHANGE: Updates to `loader-utils@^1.1.0` &  `loderUtils.getOptions`

Author: shellscape

.travis.yml

@@ -7,16 +7,13 @@ matrix:
   fast_finish: true
   include:
     - os: linux
-      node_js: '6'
+      node_js: '8'
       env: JOB_PART=test
     - os: linux
-      node_js: '4.3'
-      env: JOB_PART=test
-    - os: linux
-      node_js: '7'
+      node_js: '9'
       env: JOB_PART=test
 before_install:
   - nvm --version
   - node --version
 script:
-  - yarn run travis:$JOB_PART
+  - npm run travis:$JOB_PART