Could --biblatex use autocite instead of autocites so as to support numeric-comp style?

[jiewuza <jiewuza-9Onoh4P/yGk@public.gmane.org>]

With --biblatex, this md file:
```
We are citing [@A1; @A2; @A3]
```

is converted into tex: (autocites version)
```
We are citing \autocites{A1}{A2}{A3}
```

instead of (autocite version)
```
We are citing \autocite{A1,A2,A3}
```

I did not notice the difference until I add numeric-comp style.

For autocite version:
```
\usepackage[style=numeric-comp]{biblatex}
...
We are citing \autocite{A1,A2,A3}
```
The result pdf is what I expected, it shows as
`We are citing [1-3]`.

While for autocites version, it shows as
`We are citing [1,2,3]`, not compressed.