Add command fails on windows

When I try to add twig using

perseus add "twig/twig"

I get a warning

Failed to retrieve information about package "twig/twig" from Packagist. Called https://packagist.org/packages%5Ctwig%5Ctwig.json. Error: Expected a return code within 2xx for package "twig/twig". Got 404

It seems that the %5C escapes are not accepted by packagist anymore as

https://packagist.org/packages%5Ctwig%5Ctwig.json

returns the requested json

## Expected Behavior

Should just work

## Current Behavior

Fails to retrieve the package description.

## Possible Solution

## Steps to Reproduce (for bugs)

1. run perseus add "twig/twig" on windows.

## Context

## Your Environment

* Version used (`perseus version`):
* Operating System and version:
* Medusa configuration:
* Satis configuration: