Update to 3.0.0

- Add fromJson factories for all objects
- Make some properties use getters, to reduce redundant data
- Make all objects comparable with the equatable package
- Make all objects immutable with a constant constructor
    as a result of making them comparable

example/api/kanji_search.dart

@@ -7,6 +7,7 @@ void main() {
 
     final data = result.data;
     if (data != null) {
+      print('Kanji: ${data.kanji}');
       print('Taught in: ${data.taughtIn}');
       print('JLPT level: ${data.jlptLevel}');
       print('Newspaper frequency rank: ${data.newspaperFrequencyRank}');

example/api/phrase_search.dart

@@ -4,7 +4,6 @@ final JsonEncoder encoder = JsonEncoder.withIndent('  ');
 
 void main() {
   jisho.searchForPhrase('日').then((result) {
-  // jisho.searchForPhrase('する').then((result) {
     print(encoder.convert(result));
   });
 }