Use canonical path for file input value

[robertfausk]

Also see #26 and #9

Executing the test suite with panther gives following result:

There was 1 error:

1) Behat\Mink\Tests\Driver\Custom\Js\ChangeEventTest::testSetValueChangeEvent with data set "file" ('the-file', '/var/www/html/vendor/mink/dri...e1.txt', '/var/www/html/vendor/mink/dri...e2.txt')
Facebook\WebDriver\Exception\UnknownServerException: unknown error: path is not canonical: /var/www/html/vendor/mink/driver-testsuite/tests/Js/../../web-fixtures/file1.txt

[robertfausk]

Otherwise this could also be handled in specific driver implementation to be more fail save.

E.g. something like:

    public function setValue($xpath, $value)
    {
        // ...

        // add workaround for now in case value is not a canonical path
        if ('input' === $element->getTagName() && 'file' === $element->getAttribute('type')) {
            $realpathValue = \realpath($value);
            $value = \is_string($realpathValue) ? $realpathValue : $value;
        }

		// ...
	}

@stof @aik099 What do you think?

[stof]

IMO, we should not force users to provide a canonical path. If a driver has this requirement internally, it should perform the canonicalization.

[robertfausk]

Alright. I'm fine with this. Closing then:)