chore(package): update eslint to version 5.15.2

Closes #55

Author: greenkeeper[bot]

package.json

@@ -45,7 +45,7 @@
 	"devDependencies": {
 		"@commitlint/cli": "^7.0.0",
 		"@commitlint/config-conventional": "^7.0.1",
-		"eslint": "~4.19.0",
+		"eslint": "~5.15.2",
 		"eslint-plugin-wordpress": "git://github.com/WordPress-Coding-Standards/eslint-plugin-wordpress.git#552af1454d175e15f6d25aadc2ccde30a1922d4f",
 		"husky": "~1.3.0",
 		"is-plain-obj": "~1.1.0",