Don't ask escaping for boolean attributes at the beginning of attributes-list (#2956)

* Update tests: Don't ask escaping for the first boolean attribute

* Don't ask escaping for the first attribute w/o value

Author: ezhlobo

packages/pug-lexer/index.js

@@ -1019,7 +1019,7 @@ Lexer.prototype = {
       var whitespaceRe = /[ \n\t]/;
       var quoteRe = /['"]/;
 
-      var escapedAttr = true
+      var escapedAttr = false
       var key = '';
       var val = '';
       var state = characterParser.defaultState();

packages/pug-lexer/test/__snapshots__/index.test.js.snap

@@ -634,7 +634,7 @@ Array [
   Object {
     "col": 3,
     "line": 3,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "foo",
     "type": "attribute",
     "val": true,
@@ -808,7 +808,7 @@ Array [
   Object {
     "col": 10,
     "line": 8,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "selected",
     "type": "attribute",
     "val": true,
@@ -985,7 +985,7 @@ Array [
   Object {
     "col": 3,
     "line": 14,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "foo",
     "type": "attribute",
     "val": true,
@@ -1159,7 +1159,7 @@ Array [
   Object {
     "col": 10,
     "line": 19,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "selected",
     "type": "attribute",
     "val": true,
@@ -1318,7 +1318,7 @@ Array [
   Object {
     "col": 5,
     "line": 25,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -1355,7 +1355,7 @@ Array [
   Object {
     "col": 5,
     "line": 27,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -1392,7 +1392,7 @@ Array [
   Object {
     "col": 5,
     "line": 29,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -1429,7 +1429,7 @@ Array [
   Object {
     "col": 5,
     "line": 31,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -1466,7 +1466,7 @@ Array [
   Object {
     "col": 5,
     "line": 33,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -1503,7 +1503,7 @@ Array [
   Object {
     "col": 5,
     "line": 35,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "abc",
     "type": "attribute",
     "val": true,
@@ -16354,7 +16354,7 @@ Array [
   Object {
     "col": 21,
     "line": 7,
-    "mustEscape": true,
+    "mustEscape": false,
     "name": "something",
     "type": "attribute",
     "val": true,