composer: packages installed globally, variables reorganisation
metadata: version for all dependent cookbooks specified

This fixes often situation when dependent cookbook introduced major changes, which causes whole recipe not working anymore.
Ruby: fix default system ruby interferences with Chef's embedded ruby
mysql recipe: migrate to newest 5.x

It has redesigned architecture, all so called tuneable options were dropped and now they have to be configured via extra .cnf file.
Cosmetics, README update
nginx: cleaning some artefacts in /var/www/*
MySQL: making sure utf8 is always used. Non-used log file removed.
Version bumped to 0.4.0, change log updated
Conflicted Vagrantfile merged