Remove deprecated twitter handle.
 Merge branch 'remove-old-twitter' into 'master'

Remove Old Twitter
Use 6-5 branch in installation docs

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Version 6.5.0

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