feat(default filter): Support multiple defaults

Sources/Filters.swift

@@ -33,7 +33,17 @@ func lowercase(_ value: Any?) -> Any? {
 }
 
 func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
-  return value ?? arguments.first as Any
+  if let value = value {
+    return value
+  }
+
+  for argument in arguments {
+    if let argument = argument {
+      return argument
+    }
+  }
+
+  return nil
 }
 
 func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {

Tests/StencilTests/FilterSpec.swift

@@ -101,6 +101,12 @@ func testFilter() {
       let result = try template.render(Context(dictionary: [:]))
       try expect(result) == "Hello World"
     }
+
+    $0.it("supports multiple defaults") {
+      let template = Template(templateString: "Hello {{ name|default:a,b,c,\"World\" }}")
+      let result = try template.render(Context(dictionary: [:]))
+      try expect(result) == "Hello World"
+    }
   }
 
   describe("join filter") {