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Fix for exception thrown in Request::__toString() method.

Changed composer.json to not use fixed versions anymore.

This moved to be only a bundle. Server and client are now in separated libraries/repositories.

• Using beta versions of server and client.

• This moved to be only a bundle. Server and client are now in separated libraries/repositories.
• Still under test.
• Still no code freeze for version 2.0

PR from @Gounlaf - #52

Pull request #49

Fixes https://github.com/mcustiel/phiremock/issues/44 (RequestBuilder: andPriority doesnt not return $this) Thanks to @Gounlaf

Solves issue #43