Add configuration for stylus to import custom files

There is a file `common.styl` that contains functions and variables. It has imported almost to every file:

``` coffeescript
@import "common//base/common"
```

Sometimes developers forget to import the file, especially for new widgets or when they split up one huge widget to several widgets.

It would be helpful to import `common.styl` to all files automatically, like it is with _Nib_ library.
