Add support of the Windows OS

1.2

Allow to add additional env reader, nor replace existing

1.1

Fix tests

1.0

Testing in Behat environment:

• Created two extensions for testing which are used this autoloader.
• Every extension has it own context with a single step.
• Configuration file contains both extensions.
• Testing feature contains both steps from both extensions.
• All these staff executes as PHPUnit test.