Restructure repo for two asssemblers

[scotws]

Once we are switched to 64tass, we're going to have two versions of Tali, one with the old assembler Ophis, which I would only keep for bug fixes, and one with the new assembler 64tass, which would be the active. This is probably a good time to give this repo a more formal structure with stuff like stable and master branches (see https://gist.github.com/digitaljhelms/4287848 for example).

My current idea would be a master-ophis for the current Ophis version that will stick around for bug fixes - not everybody will want to switch - and master and stable for 64tass. Since I've never done this before, I'd be grateful for suggestions. Also, we need to not screw things up too bad for the people who have currently branched from master (Ophis) and will find themselves with a (no pun intended) new master. I'm sure this can't be a new problem?

[scotws]

@SamCoVT For the moment, I've put the 64tass stuff in master-64tass. Having done that, I'm wondering if that is asking for hurt with typos, so I might rename it to something that doesn't start with "master". Let's first see if this works as a base for you.

[SamCoVT]

Let leave things as they are for right now and look to re-arrange things with a "v1.1" release where the tass version will become "master". I'll be working off your master-64tass branch for now. I agree that it would be good to keep a branch for the old Ophis version as there are a few people who have heavily customized that version.