Typescript translate relative paths to absolute paths

| 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 already opened PR for this https://github.com/kriswallsmith/assetic/pull/374 without any new activity for more than one 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" />
```