refs #140: migrate autoload to psr-4

[rvitaliy]

Closes #140

• i moved some classes to own file, in order to make code compatible with psr-4.
  NOTE: no logics are impacted with this PR.

• i don't move it to an own namespace to not generate BC.

• i don't configure autoload for dev, because we currently have nothing to load

[rvitaliy]

@JakubOnderka

1. i see you have already one PR for this think PSR-4 #122 but you move classes to namespaces i think it's a BC changes.
2. https://ci.appveyor.com/project/JakubOnderka/php-parallel-lint/builds/26336175 i can't understand why CI of appveyor is breaking

[rvitaliy]

I close this PR, because this repo is abandoned.