#98 Fix for newer rar formats unsupported by unar

[laf]

Newer rar format in winrar on windows are not properly supported by the unar package in linux. So what happens is the window freezes and this is annoying and unacceptable. However requiring non-free package is also unacceptable.

Solution:

Parse rar to detail rar version and if rar version is not 100% supported by unar then do not extract with unar and post message saying that the non-free unrar package is required to properly extract this particular file.