Allow trailing spaces in code blocks

lib/md009.js

@@ -30,9 +30,11 @@ module.exports = {
       listItemLineNumbers.sort((a, b) => a - b);
     }
     const expected = (brSpaces < 2) ? 0 : brSpaces;
-    forEachLine(lineMetadata(), (line, lineIndex) => {
+    let inFencedCode = 0;
+    forEachLine(lineMetadata(), (line, lineIndex, inCode, onFence) => {
+      inFencedCode += onFence;
       const lineNumber = lineIndex + 1;
-      if (trailingSpaceRe.test(line) &&
+      if ((!inCode || inFencedCode !== 0) && trailingSpaceRe.test(line) &&
         !includesSorted(listItemLineNumbers, lineNumber)) {
         const actual = line.length - line.trimRight().length;
         if (expected !== actual) {

test/code_block_fenced.md

@@ -9,9 +9,16 @@ And here is more text
 This is a code block that won't trigger.
 ```
 
+```text
+This is code
+ 
+with an empty line.
+```
+
 But we'll do another:
 
     And this {MD046}
     will.
 
 Final text is here
+{MD009:14}

test/code_block_indented.md

@@ -14,4 +14,8 @@ But we'll do another:
     And this
     will.
 
-Final text is here
+One last one:
+
+    This is code
+    
+    with an empty indented line.

test/trailing_spaces_br.md

@@ -1,4 +1,6 @@
 This line has a single trailing space {MD009} 
 This line has two trailing spaces and should be allowed  
 This line has three trailing spaces {MD009}   
+ 
+{MD009:4}
 This line has four trailing spaces {MD009}