Invalid signedUrl when filename contains parantheses

AWS S3 returns SignatureDoesNotMatch error because it asks for %28 and %29 in StringToSign but the Client.prototype.signedUrl function (https://github.com/LearnBoost/knox/blob/master/lib/client.js#L858) does not URL-encode "()" characters

Start in lib/client.js at the signedUrl function around line 858 and inspect how filenames are encoded before signing. Reproduce the issue with a filename containing parentheses, then verify that the generated URL and StringToSign use the expected encoding and that S3 no longer returns SignatureDoesNotMatch.

Written by the indexing model from the issue text.