Do not quote the "class" key

Quoting reserved words in property names is not needed since dropping
support of IE < 9.

lib/compiler/asts.js

@@ -65,7 +65,7 @@ let asts = {
         return node.value !== "";
       },
 
-      "class": consumesTrue,
+      class: consumesTrue,
       any: consumesTrue
     });
 

lib/compiler/passes/generate-bytecode.js

@@ -567,7 +567,7 @@ function generateBytecode(ast) {
       }
     },
 
-    "class": function(node) {
+    class: function(node) {
       let regexp = "/^["
         + (node.inverted ? "^" : "")
         + node.parts.map(part =>

lib/compiler/passes/generate-js.js

@@ -771,7 +771,7 @@ function generateJS(ast, options) {
       "      return \"\\\"\" + literalEscape(expectation.text) + \"\\\"\";",
       "    },",
       "",
-      "    \"class\": function(expectation) {",
+      "    class: function(expectation) {",
       "      var escapedParts = expectation.parts.map(function(part) {",
       "        return Array.isArray(part)",
       "          ? classEscape(part[0]) + \"-\" + classEscape(part[1])",

lib/compiler/visitor.js

@@ -56,7 +56,7 @@ let visitor = {
       semantic_not: visitNop,
       rule_ref: visitNop,
       literal: visitNop,
-      "class": visitNop,
+      class: visitNop,
       any: visitNop
     };
 

lib/parser.js

@@ -32,7 +32,7 @@ peg$SyntaxError.buildMessage = function(expected, found) {
       return "\"" + literalEscape(expectation.text) + "\"";
     },
 
-    "class": function(expectation) {
+    class: function(expectation) {
       var escapedParts = expectation.parts.map(function(part) {
         return Array.isArray(part)
           ? classEscape(part[0]) + "-" + classEscape(part[1])

spec/unit/parser.spec.js

@@ -156,7 +156,7 @@ describe("PEG.js grammar parser", function() {
       semantic_not: stripLeaf,
       rule_ref: stripLeaf,
       literal: stripLeaf,
-      "class": stripLeaf,
+      class: stripLeaf,
       any: stripLeaf
     });