Bump dependencies (#29)

* Bump symfony/flex

Changelogs summary:

 - symfony/flex updated from v1.0.80 to v1.0.89
   See changes: symfony/flex@v1.0.80...v1.0.89
   Release notes: https://github.com/symfony/flex/releases/tag/v1.0.89

* Bump symfony/http-foundation

Remove known vulnerabilities:

 - CVE-2018-14773: CVE-2018-14773: Remove support for legacy and risky HTTP headers
  https://symfony.com/blog/cve-2018-14773-remove-support-for-legacy-and-risky-http-headers

Changelogs summary:

 - symfony/http-foundation updated from v4.1.1 to v4.1.3
   See changes: symfony/http-foundation@v4.1.1...v4.1.3
   Release notes: https://github.com/symfony/http-foundation/releases/tag/v4.1.3

Author: roukmoute