rework

I've basically rewrote your module so that it works with @yields changes on the newest builder (0.12.0).

If you would merge this the basic usage will be:
```javascript
// Build templates.
builder.use(jade());
builder.use(commonjs('templates'));
builder.use(concat('templates'));
```

component-jade will compile to plain html if you set `opts.plain` to true
```javascript
builder.use(jade(true))
```
Otherwise it would compile to templates like it did before.

Also, jade and the runtime.js are now __not__ included in the module itself, instead they must be added as dependencies.

If you don't like any of those changes you can simply ignore this PR :) I will add tests and update the readme as soon as it gets accepted.