Adding STDIN support
feature #310 Adding STDIN support (davividal)

This PR was squashed before being merged into the 0.4.x-dev branch (closes #310).

Discussion
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Adding STDIN support

Add support to `cat foo.php | php-cs-fixer`. When using `STDIN`, the `dry-run` option will be set to `true`.

Commits
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e475a72 Adding STDIN support
fixed previous merge