Remove docs and tests for duffle.toml and duffle.yaml

docs/proposal/203-duffle-build.md

@@ -1,5 +1,5 @@
 # Duffle Build
 
-This document describes how `duffle build` works, and how it uses the duffle build file: `duffle.json, duffle.yaml, duffle.toml`.
+This document describes how `duffle build` works, and how it uses the duffle build file: `duffle.json`.
 
-`duffle build` take a path to a directory that contains a duffle build file (`duffle.json, duffle.toml, or duffle.yaml`) to build a Cloud Native Application Bundle (CNAB). In the process, it also builds all of the invocation images specified in the duffle build file.
+`duffle build` take a path to a directory that contains a duffle build file (`duffle.json`) to build a Cloud Native Application Bundle (CNAB). In the process, it also builds all of the invocation images specified in the duffle build file.

pkg/duffle/manifest/manifest_test.go

@@ -28,7 +28,7 @@ func TestGenerateName(t *testing.T) {
 }
 
 func TestLoad(t *testing.T) {
-	testcases := []string{"", "duffle.toml", "duffle.json", "duffle.yaml"}
+	testcases := []string{"", "duffle.json"}
 
 	for _, tc := range testcases {
 		t.Run(tc, func(t *testing.T) {