Fix and improve literal mode.

  * Require a blank line as delimiter between text and code.
  * Don't ignore indentation with mixed whitespace.
  * Handle blank lines depending on preceding lines.
    (Addresses changes in jashkenas#190.)
  * Bonus: Remove unused variable (leftover from jashkenas#190).

docco.litcoffee

@@ -126,24 +126,25 @@ invert the prose and code relationship on a per-line basis, and then continue as
 normal below.
 
       if lang.literate
+        isText = maybeCode = yes
         for line, i in lines
-          lines[i] = if /^\s*$/.test line
-            ''
-          else if match = (/^([ ]{4}|\t)/).exec line
+          lines[i] = if maybeCode and match = /^([ ]{4}|[ ]{0,3}\t)/.exec line
+            isText = no
             line[match[0].length..]
+          else if maybeCode = /^\s*$/.test line
+            if isText then lang.symbol else ''
           else
+            isText = yes
             lang.symbol + ' ' + line
 
       for line in lines
         if line.match(lang.commentMatcher) and not line.match(lang.commentFilter)
           save() if hasCode
           docsText += (line = line.replace(lang.commentMatcher, '')) + '\n'
           save() if /^(---+|===+)$/.test line
-          prev = 'text'
         else
           hasCode = yes
           codeText += line + '\n'
-          prev = 'code'
       save()
 
       sections