Add oneline test

test/rendering/oneline_url.mml

@@ -0,0 +1,15 @@
+{
+    "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+    "Stylesheet": [
+        "oneline_url.mss"
+    ],
+    "Layer": [{
+        "class": "new",
+        "name": "countries",
+        "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+        "Datasource": {
+            "file": "http://tilemill-data.s3.amazonaws.com/test_data/shape_demo.zip",
+            "type": "shape"
+        }
+    }]
+}

test/rendering/oneline_url.mss

@@ -0,0 +1 @@
+#countries { one/marker-file: url(http://upload.wikimedia.org/wikipedia/commons/7/72/Cup_of_coffee.svg); }

test/rendering/oneline_url.result

@@ -0,0 +1,5 @@
+<Style name="layer" filter-mode="first" >
+  <Rule>
+    <MarkersSymbolizer file="http://upload.wikimedia.org/wikipedia/commons/7/72/Cup_of_coffee.svg" />
+  </Rule>
+</Style>