fix: update dependencies (#245)

* chore: update some dependencies
* chore: add yarn.lock, update gitignore
* chore: update xo, fix or add rules
* chore: remove orphaned jshint file
* chore: cleanup package.json, add correct version
* chore: update dependencies
* build: update devDependencies
* chore: update npmignore
* build: use node >= 6
* chore: update dependencies, decrease semantic-release
* build: fix linting with node >=6
* build: update devDependencies
* build: update dependencies
* build: fix travis build
* build: update dependencies, revert version "fix" :-)

Author: rejas

.gitignore

@@ -1,3 +1,5 @@
 .DS_Store
 node_modules/
 temp/
+npm-debug.log
+yarn-error.log

.jshintrc

@@ -1,4 +1,5 @@
 .*
+.idea
 src/inject/expected/
 src/inject/fixtures/
 src/inject/*_test.js

.npmignore

@@ -1,13 +1,10 @@
 language: node_js
-cache:
-  directories:
-    - node_modules
 notifications:
   email: false
 node_js:
+  - '10'
   - '8'
   - '6'
-  - '4'
 env:
   - BUILD_LEADER_ID=4
 branches:
@@ -24,4 +21,3 @@ jobs:
         - test $TRAVIS_BRANCH = "master" && test $TRAVIS_PULL_REQUEST = "false"
         - echo "//registry.npmjs.org/:_authToken=${NPM_TOKEN}" > .npmrc
         - npm run semantic-release
-