Fix multi matters w/ the same first character

Closes GH-2.

lib/syntax.js

@@ -8,10 +8,16 @@ function create(options) {
   var index = -1
   var flow = {}
   var matter
+  var code
 
   while (++index < length) {
     matter = settings[index]
-    flow[fence(matter, 'open').charCodeAt(0)] = parse(matter)
+    code = fence(matter, 'open').charCodeAt(0)
+    if (code in flow) {
+      flow[code].push(parse(matter))
+    } else {
+      flow[code] = [parse(matter)]
+    }
   }
 
   return {flow: flow}

test.js

@@ -6,6 +6,7 @@ var html = require('./html')
 var custom = {type: 'custom', marker: {open: '<', close: '>'}}
 var json = {type: 'json', fence: {open: '{', close: '}'}}
 var yamlAnywhere = {type: 'yaml', marker: '-', anywhere: true}
+var customAndYaml = [{type: 'custom', marker: {open: '-', close: '.'}}, 'yaml']
 
 test('core', function (t) {
   t.throws(
@@ -232,5 +233,14 @@ test('markdown -> html (micromark)', function (t) {
     'should not support custom matters in the middle'
   )
 
+  t.deepEqual(
+    micromark('---\nasd\n...', {
+      extensions: [syntax(customAndYaml)],
+      htmlExtensions: [html(customAndYaml)]
+    }),
+    '',
+    'should not support custom matters in the middle'
+  )
+
   t.end()
 })