Cleaned up before_script.sh so that it was possible to reuse it for Vagrant

I have completely reworked the current `before_script.sh` so that it was possible to reuse it with `Vagrant`

At this moment the `Vagrant`-driven environment **completely** reproduces results on `travis-ci`

    vagrant@precise32:~$ cd /vagrant/
    vagrant@precise32:/vagrant$ vendor/bin/phpunit Tests
    PHPUnit 3.7.37 by Sebastian Bergmann.

    Configuration read from /vagrant/phpunit.xml.dist

    I.............SSSSSSSSSSSSSSSSSSSSSS..........SSSS......I......  63 / 237 ( 26%)

    .............I....................................I........II.. 126 / 237 ( 53%)

    ....I....I...........II.IIIII.............I.................... 189 / 237 ( 79%)

    ..................I................I............

    Time: 4.06 minutes, Memory: 18.25Mb

    OK, but incomplete or skipped tests!
    Tests: 237, Assertions: 506, Incomplete: 18, Skipped: 26.

### How to use

    vagrant up
    # then it's recommended to increase RAM and CPUs (see the note below)

    vagrant ssh
    
    cd /vagrant
    vendor/bin/phpunit Tests

### **IMPORTANT NOTE**
after `vagrant` has initialized the VM it makes sense to change amount of memory (and number of CPUs) manually from 384Mb by default to something near 2Gb (and 2 CPUs accordingly). I did nto do that in `Vagrantfile` deliberately since not every configuration might afford allocating 2Gb and 2 CPUs. Otherwise VM will swap hardly and at least one test will crash due to Out Of Memory.