added link to correct spotify install instructions
added link to correct spotify install instructions

Blockify requires Spotify > 1.0.12. If you install Spotify via https://www.spotify.com/nl/download/linux/, you end up with an old version and blockify does not work (tested on Ubuntu 14.04).
As a fix, use the official instructions for the beta spotify version; https://community.spotify.com/t5/Spotify-Community-Blog/Spotify-Client-1-x-beta-for-Linux-has-been-released/ba-p/1147084.
It would be nice if the blockify manual was updated and outlines how to install spotify or links to the correct instructions.
serialoverflow/blockify,mikar/blockify