Roll Observatory packages and add a roll script

packages/petitparser/lib/src/json/parser.dart

-part of json;
+part of petitparser.json;
 
-/**
- * JSON parser.
- */
+/// JSON parser.
 class JsonParser extends GrammarParser {
   JsonParser() : super(const JsonParserDefinition());
 }
 
-/**
- * JSON parser definition.
- */
+/// JSON parser definition.
 class JsonParserDefinition extends JsonGrammarDefinition {
   const JsonParserDefinition();
 
   array() => super.array().map((each) => each[1] != null ? each[1] : new List());
   object() => super.object().map((each) {
     var result = new LinkedHashMap();
     if (each[1] != null) {
       for (var element in each[1]) {
         result[element[0]] = element[2];
       }
     }
     return result;
   });
 
   trueToken() => super.trueToken().map((each) => true);
   falseToken() => super.falseToken().map((each) => false);
   nullToken() => super.nullToken().map((each) => null);
   stringToken() => ref(stringPrimitive).trim();
   numberToken() => super.numberToken().map((each) {
     var floating = double.parse(each);
     var integral = floating.toInt();
     if (floating == integral && each.indexOf('.') == -1) {
       return integral;
     } else {
       return floating;
     }
   });
 
   stringPrimitive() => super.stringPrimitive().map((each) => each[1].join());
-  characterEscape() => super.characterEscape().map((each) => JSON_ESCAPE_CHARS[each[1]]);
-  characterOctal() => super.characterOctal().map((each) {
-    throw new UnsupportedError('Octal characters not supported yet');
+  characterEscape() => super.characterEscape().map((each) => jsonEscapeChars[each[1]]);
+  characterUnicode() => super.characterUnicode().map((each) {
+    var charCode = int.parse(each[1].join(), radix: 16);
+    return new String.fromCharCode(charCode);
   });
-
 }