Added a default logger for the user profile builder.

Author: alda-optimizely

OptimizelySDKUserProfile/OptimizelySDKUserProfile/OPTLYUserProfileBuilder.m

@@ -34,4 +34,11 @@ - (id)initWithBlock:(OPTLYUserProfileBuilderBlock)block {
     return self;
 }
 
+- (id<OPTLYLogger>)logger {
+    if (!_logger) {
+        _logger = [[OPTLYLoggerDefault alloc] initWithLogLevel:OptimizelyLogLevelAll];
+    }
+    return _logger;
+}
+
 @end