Fix type name for GeoShape mapping

Closes #925

Author: gmarz

src/Nest/Domain/Mapping/Types/GeoShapeMapping.cs

@@ -10,9 +10,8 @@ public class GeoShapeMapping : IElasticType
 	{
 		public PropertyNameMarker Name { get; set; }
 
-		private TypeNameMarker __type;
 		[JsonProperty("type")]
-		public virtual TypeNameMarker Type { get { return (TypeNameMarker)(__type ?? "point"); } set { __type = value; } }
+		public virtual TypeNameMarker Type { get { return new TypeNameMarker { Name = "geo_shape" }; } }
 
 		[JsonProperty("similarity")]
 		public string Similarity { get; set; }

src/Tests/Nest.Tests.Unit/Core/Map/Properties/GeoShapeProperty.json

@@ -2,7 +2,7 @@
   "elasticsearchprojects": {
     "properties": {
       "myGeoShape": {
-        "type": "point",
+        "type": "geo_shape",
         "tree": "geohash",
         "tree_levels": 2,
         "distance_error_pct": 0.025