Integrated Distill library

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #20
| License       | MIT
| Doc PR        | -

The installer now integrates the [Distill library](https://github.com/raulfraile/distill) to download the best format (ZIP or TGZ) and to uncompress it using the native operating system commands:

![symfony-installer](https://cloud.githubusercontent.com/assets/73419/5088468/330ba72c-6f34-11e4-9fdc-89e462dd296b.gif)
Something strange happens to me. On the console I don't see the two white spaces, but when I copy+paste the text contents of the command output, the two white spaces are there:

```
$ php symfony new blog

 Downloading Symfony...
    4.74 MB/4.74 MB [▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓] 100%

 Preparing project...

 ✔  Symfony was successfully installed. Now you can:

    * Configure your application in blog/app/config/parameters.yml file.

    * Run your application:
        1. Execute the php blog/app/console server:run command.
        2. Browse to the http://localhost:8000 URL.

    * Read the documentation at http://symfony.com/doc
```

On the console I can only see one white space (iTerm2, Mac Os X):

![console_command_output](https://cloud.githubusercontent.com/assets/73419/5090484/bc013cbe-6f42-11e4-92bb-b3f6e6487de6.png)