fix: UrlTileSource.Builder was hiding zoom values from TileSource.Builder

- values set thorugh builder.minZoom()/maxZoom() were ignored

should fix: #120

vtm-tests/test/org/oscim/tiling/source/bitmap/BitmapTileSourceTest.java

@@ -5,6 +5,7 @@ import static org.fest.assertions.api.Assertions.assertThat;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
+import org.oscim.layers.tile.bitmap.BitmapTileLayer.FadeStep;
 import org.oscim.tiling.ITileDataSource;
 import org.oscim.tiling.source.HttpEngine;
 import org.oscim.tiling.source.LwHttp;
@@ -43,6 +44,21 @@ public class BitmapTileSourceTest {
 		Mockito.verify(okHttp).close();
 	}
 
+	@Test
+	public void shouldUseBuilderConfig() {
+		BitmapTileSource ts = BitmapTileSource.builder()
+		    .url("http://example.com")
+		    .zoomMax(42)
+		    .zoomMin(23)
+		    .fadeSteps(new FadeStep[] { new FadeStep(0, 10, 0.5f, 1.0f) })
+		    .build();
+
+		assertThat(ts.getUrl().getHost()).isEqualTo("example.com");
+		assertThat(ts.getZoomLevelMin()).isEqualTo(23);
+		assertThat(ts.getZoomLevelMax()).isEqualTo(42);
+		assertThat(ts.getFadeSteps()).isNotNull();
+	}
+
 	/**
 	 * Test factory that allows the specific {@link HttpEngine} instance to be
 	 * set.