Some dart linter fixes (#171)

Author: chrbayer

lib/src/objects/parse_acl.dart

@@ -1,7 +1,7 @@
 part of flutter_parse_sdk;
 
 /// [ParseACL] is used to control which users can access or modify a particular object
-/// [ParseObject] can have its own [ParceACL]
+/// [ParseObject] can have its own [ParseACL]
 /// You can grant read and write permissions separately to specific users
 ///  or you can grant permissions to "the public" so that, for example, any user could read a particular object but
 /// only a particular set of users could write to that object
@@ -126,8 +126,8 @@ class _ACLPermissions {
   _ACLPermissions(this._readPermission, this._writePermission);
   final String _keyReadPermission = 'read';
   final String _keyWritePermission = 'write';
-  bool _readPermission;
-  bool _writePermission;
+  final bool _readPermission;
+  final bool _writePermission;
 
   bool getReadPermission() {
     return _readPermission;

lib/src/objects/parse_installation.dart

@@ -206,15 +206,15 @@ class ParseInstallation extends ParseObject {
   ///Subscribes the device to a channel of push notifications.
   void subscribeToChannel(String value) {
     final List<dynamic> channel = <String>[value];
-    // ignore: deprecated_member_use_from_same_package
-    addUnique('channels', channel);
+    setAddUnique('channels', channel);
+    save();
   }
 
   ///Unsubscribes the device to a channel of push notifications.
   void unsubscribeFromChannel(String value) {
     final List<dynamic> channel = <String>[value];
-    // ignore: deprecated_member_use_from_same_package
-    removeAll('channels', channel);
+    setRemove('channels', channel);
+    save();
   }
 
   ///Returns an <List<String>> containing all the channel names this device is subscribed to.