deprecate substr method and use existing strip function in grammar

lib/handlebars/compiler/helpers.js

@@ -24,7 +24,7 @@ export function SourceLocation(source, locInfo) {
 
 export function id(token) {
   if (/^\[.*\]$/.test(token)) {
-    return token.substr(1, token.length - 2);
+    return token.substring(1, token.length - 1);
   } else {
     return token;
   }

src/handlebars.l

@@ -4,7 +4,7 @@
 %{
 
 function strip(start, end) {
-  return yytext = yytext.substr(start, yyleng-end);
+  return yytext = yytext.substring(start, yyleng - end + start);
 }
 
 %}
@@ -59,7 +59,7 @@ ID    [^\s!"#%-,\.\/;->@\[-\^`\{-~]+/{LOOKAHEAD}
                                   if (this.conditionStack[this.conditionStack.length-1] === 'raw') {
                                     return 'CONTENT';
                                   } else {
-                                    yytext = yytext.substr(5, yyleng-9);
+                                    strip(5, 9);
                                     return 'END_RAW_BLOCK';
                                   }
                                  }