Localizations break when values/keys contain quotes

[kix]

Given this:

use Passbook\Pass\Localization;
$localization = new Localization('en');
$localization->addStrings([
    'SOME_FIELD' => 'This "has" "quotes"',
]);

...the expected en.lproj/pass.strings is supposed to have this line:

"SOME_FIELD" = "This \"has \"quotes\"";

...yet the quotes are ignored and the pass.strings file gets malformed, which, in turn, makes a part of the translations invalid:

"SOME_FIELD" = "This "has "quotes"";
"SOME_OTHER_FIELD"="Test test";

If I had some of the fields after this faulty one, those would be broken too. I suggest adding an addslashes() call somewhere, for example in the Localization#getStringsFileOutput() method.