Unifying MD5 and sha goodie answers

Changes in this PR:

* Adds padding to base64 encoded hashes in md5 and sha goodies, because the base64 goodie pads its output as well. This way they're more similar.
* Adds html ouput to the sha goodie that looks the same way as the current ouput from the MD5 one.
* Adds a test file for the sha goodie, I couldn't find one from before.
* Code style, use early return guard instead of large if block when handling query. I was asked to do a  similar change earlier, and it looks clearer.

Yes, the length is supposed to be a multiple of four. But since the hashes are of constant length, the right amount of '=' is always going to be two.