Use 'Nan::Set'

Fix the following errors.

```
../src/main.cc:138:25: error: no matching member function for call to 'Set'
      misspelled_range->Set(Nan::New("end").ToLocalChecked(), Nan::New<Integer>(end));
```

Author: abetomo

src/main.cc

@@ -135,9 +135,9 @@ class Spellchecker : public Nan::ObjectWrap {
       uint32_t start = iter->start, end = iter->end;
 
       Local<Object> misspelled_range = Nan::New<Object>();
-      misspelled_range->Set(context, Nan::New("start").ToLocalChecked(), Nan::New<Integer>(start));
-      misspelled_range->Set(context, Nan::New("end").ToLocalChecked(), Nan::New<Integer>(end));
-      result->Set(context, index, misspelled_range);
+      Nan::Set(misspelled_range, Nan::New("start").ToLocalChecked(), Nan::New<Integer>(start));
+      Nan::Set(misspelled_range, Nan::New("end").ToLocalChecked(), Nan::New<Integer>(end));
+      Nan::Set(result, index, misspelled_range);
     }
   }
 
@@ -222,7 +222,7 @@ class Spellchecker : public Nan::ObjectWrap {
     Local<Array> result = Nan::New<Array>(dictionaries.size());
     for (size_t i = 0; i < dictionaries.size(); ++i) {
       const std::string& dict = dictionaries[i];
-      result->Set(context, i, Nan::New(dict.data(), dict.size()).ToLocalChecked());
+      Nan::Set(result, i, Nan::New(dict.data(), dict.size()).ToLocalChecked());
     }
 
     info.GetReturnValue().Set(result);
@@ -249,7 +249,7 @@ class Spellchecker : public Nan::ObjectWrap {
       const std::string& word = corrections[i];
 
       Nan::MaybeLocal<String> val = Nan::New<String>(word.data(), word.size());
-      result->Set(context, i, val.ToLocalChecked());
+      Nan::Set(result, i, val.ToLocalChecked());
     }
 
     info.GetReturnValue().Set(result);

src/worker.cc

@@ -36,9 +36,9 @@ void CheckSpellingWorker::HandleOKCallback() {
     uint32_t start = iter->start, end = iter->end;
 
     Local<Object> misspelled_range = Nan::New<Object>();
-    misspelled_range->Set(context, Nan::New("start").ToLocalChecked(), Nan::New<Integer>(start));
-    misspelled_range->Set(context, Nan::New("end").ToLocalChecked(), Nan::New<Integer>(end));
-    result->Set(context, index, misspelled_range);
+    Nan::Set(misspelled_range, Nan::New("start").ToLocalChecked(), Nan::New<Integer>(start));
+    Nan::Set(misspelled_range, Nan::New("end").ToLocalChecked(), Nan::New<Integer>(end));
+    Nan::Set(result, index, misspelled_range);
   }
 
   Local<Value> argv[] = { Nan::Null(), result };