Enable html_escape for code blocks highlighted in markdown

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
html_escape is private for rails 4.0.2 :(

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
 Merge branch '6-6-4-patch' into '6-6-stable'

6-6-4 Patch
Version 6.6.4

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>