Proper class names for diff files

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Move diff css to separate file

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
New class names in notes css

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Use proper classes for sdiff content

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

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

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
 Merge branch 'file_css' into 'master'

Better css class names for diff elements