Convenience extensions for template exists

Closes #1280

Author: gmarz

src/Nest/ConvenienceExtensions/ExistsExtensions.cs

@@ -38,5 +38,14 @@ public static Task<IExistsResponse> AliasExistsAsync(this IElasticClient client,
 			return client.AliasExistsAsync(new AliasExistsRequest(indexName, aliasName));
 		}
 
+		public static IExistsResponse TemplateExists(this IElasticClient client, string templateName)
+		{
+			return client.TemplateExists(new TemplateExistsRequest(templateName));
+		}
+
+		public static Task<IExistsResponse> TemplateExistsAsync(this IElasticClient client, string templateName)
+		{
+			return client.TemplateExistsAsync(new TemplateExistsRequest(templateName));
+		}
 	}
 }

src/Tests/Nest.Tests.Integration/Indices/IndicesTemplateTests.cs

@@ -45,11 +45,11 @@ public void TemplateExistsReturnsNoFalsePositives()
 			});
 			putResponse.IsValid.Should().BeTrue();
 
-			var falseExists = this.Client.TemplateExists(new TemplateExistsRequest("hello-world-blah"));
+			var falseExists = this.Client.TemplateExists("hello-world-blah");
 			falseExists.IsValid.Should().BeTrue();
 			falseExists.Exists.Should().BeFalse();
 
-			var realExists = this.Client.TemplateExists(new TemplateExistsRequest(name));
+			var realExists = this.Client.TemplateExists(name);
 			realExists.Exists.Should().BeTrue();
 		}