Adding fixer for putting namespaces on line 2, not line 3

This PR changes code like:
"<?php

namespace X;"
to:
"<?php
namespace X;"

This is implied by all code samples provided at https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md , but is not stated in the text of the standard.
We should still remove the blank line anyway.