switch metaflac test over to comparing output against "golden" files

test/metaflac-test-files/case20-expect.meta

@@ -0,0 +1,29 @@
+METADATA block #0
+  type: 0 (STREAMINFO)
+  is last: false
+  length: 34
+  sample_rate: 8000 Hz
+  channels: 1
+  bits-per-sample: 8
+  total samples: 80000
+  MD5 signature: a042237c5493fdb9656b94a83608d11a
+METADATA block #1
+  type: 3 (SEEKTABLE)
+  is last: false
+  length: 18
+  seek points: 1
+    point 0: sample_number=0
+METADATA block #2
+  type: 4 (VORBIS_COMMENT)
+  is last: false
+  length: 74
+  comments: 1
+    comment[0]: TITLE=He_who_smelt_it_dealt_it
+METADATA block #3
+  type: 1 (PADDING)
+  is last: false
+  length: 25065
+METADATA block #4
+  type: 1 (PADDING)
+  is last: true
+  length: 0