fix db.incrObjectFieldBy for mongo

convert string to int

src/database/mongo/hash.js

@@ -231,9 +231,11 @@ module.exports = function(db, module) {
 
 	module.incrObjectFieldBy = function(key, field, value, callback) {
 		callback = callback || helpers.noop;
-		if (!key) {
+		value = parseInt(value, 10);
+		if (!key || isNaN(value)) {
 			return callback();
 		}
+
 		var data = {};
 		field = helpers.fieldToString(field);
 		data[field] = value;

tests/database/hash.js

@@ -347,7 +347,7 @@ describe('Hash methods', function() {
 
 		it('should set an objects field to 5 if object does not exist', function(done) {
 			db.incrObjectFieldBy('testObject16', 'field1', 5, function(err, newValue) {
-				assert.equal(err, null);
+				assert.ifError(err);
 				assert.equal(arguments.length, 2);
 				assert.equal(newValue, 5);
 				done();
@@ -356,12 +356,20 @@ describe('Hash methods', function() {
 
 		it('should increment an object fields by passed in value and return it', function(done) {
 			db.incrObjectFieldBy('testObject15', 'age', 11, function(err, newValue) {
-				assert.equal(err, null);
+				assert.ifError(err);
 				assert.equal(arguments.length, 2);
 				assert.equal(newValue, 111);
 				done();
 			});
 		});
+
+		it('should increment an object fields by passed in value and return it', function(done) {
+			db.incrObjectFieldBy('testObject15', 'age', '11', function(err, newValue) {
+				assert.ifError(err);
+				assert.equal(newValue, 122);
+				done();
+			});
+		});
 	});