edit install topic

- spit lines
- update for sublime text 3
Hm yes, technically ST2 and St3 aren't really parallel release channels since they are, as you said, more of separate products. ST3 isn't exactly "stable" though.

I'm thinking of this:
```
Sublime Text 3 has two release channels:

- Beta (recommended)
- Dev

Sublime Text 2 is an old and to-be-deprecated version once Sublime Text 3 is out of beta.
```

Yeah, or something similar.