Typescript reference path use real path option

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Typescript uses `<reference path="" />` to resolve dependencies on another files. This can cause problems with assetic, because assets are took out of their original place and they are put in tmp directory.

This pull request is similar to There is already opened PR for this https://github.com/kriswallsmith/assetic/pull/374 without any activity for an year.

This change allows a new setting to use real path instead of relative one. When asset is loaded, it's checked for `<reference path="">` and all paths are replaced with real paths.

``` typescript
/// <reference path="absolute.ts" />
```

is translated to

``` typescript
/// <reference path="/project/absolute.ts" />
```