More eslint fixes; eslint in php; add eslint to travis (#2419)

* Add eslint to travis.yml

* Update eslint package versions and apply new indent rules

* Enable the brace-style and block-style eslint rules

* Enable the 'curly' eslint rule

* Enable the 'keyword-spacing' eslint rule

* Enable the 'key-spacing' eslint rule

* Enable the 'object-curly-spacing' eslint rule

* Enable the 'no-new-object' eslint rule

* Only disable the no-caller eslint rule in the one affected file

* Enable the 'no-unused-vars' eslint rule for local variables

* Add linting of JS in .php files

.eslintrc.js

@@ -5,26 +5,46 @@ module.exports = {
     "browser": true,
   },
   "extends": ["google"],
+  "overrides": [{
+    // eslint-plugin-html handles eol-last slightly different - it applies to
+    // each set of script tags, so we turn it off here.
+    "files": "**/*.*php",
+    "rules": {
+      "eol-last": "off",
+      "indent": "off",
+    },
+  }],
+  "plugins": [
+    "html",
+    "php-markup",
+  ],
   "rules": {
-    "brace-style": "off",
     "camelcase": "off",
     "comma-dangle": "off",
     "guard-for-in": "off",
-    "key-spacing": "off",
     "max-len": "off",
     "new-cap": ["error", {
       capIsNewExceptions: ["Error", "Warning", "Debug", "Polygon_calcArea", "Play", "Stop"],
       newIsCapExceptionPattern: "^Asset\.."
     }],
     "no-array-constructor": "off",
-    "no-caller": "off",
-    "no-new-object": "off",
-    "no-unused-vars": "off",
+    "no-unused-vars": ["error", {
+      "vars": "local",
+      "args": "none",
+      "ignoreRestSiblings": false
+    }],
     "no-var": "off",
-    "object-curly-spacing": "off",
     "prefer-rest-params": "off",
     "quotes": "off",
     "require-jsdoc": "off",
     "spaced-comment": "off",
   },
+  "settings": {
+    "php/php-extensions": [".php"],
+    "php/markup-replacement": {"php": "", "=": "0"},
+    "php/keep-eol": false,
+    "php/remove-whitespace": false,
+    "php/remove-empty-line": false,
+    "php/remove-php-lint": false
+  },
 };