Removes also leading tab from backtick codeblock

plugins/backtick_code_block.rb

@@ -10,7 +10,7 @@ module BacktickCodeBlock
     @lang = nil
     @url = nil
     @title = nil
-    input.gsub /^`{3} *([^\n]+)?\n(.+?)\n`{3}/m do
+    input.gsub(/^`{3} *([^\n]+)?\n(.+?)\n`{3}/m) do
       @options = $1 || ''
       str = $2
 
@@ -22,8 +22,8 @@ module BacktickCodeBlock
         @caption = "<figcaption><span>#{$2}</span></figcaption>"
       end
 
-      if str.match(/\A {4}/)
-        str = str.gsub /^ {4}/, ''
+      if str.match(/\A( {4}|\t)/)
+        str = str.gsub(/^( {4}|\t)/, '')
       end
       if @lang.nil? || @lang == 'plain'
         code = tableize_code(str.gsub('<','&lt;').gsub('>','&gt;'))