Refs #20 - Update composer.lock.

Compare links for updated dependencies:
https://github.com/symfony/Console/compare/7613bbd8b0...df17996d37
https://github.com/symfony/Debug/compare/23b5f4fcad883679d9a6e1cbc568247fe606d8ee...cf012d37f7e0d059fd6b35607e99761b33ccf4ed
https://github.com/symfony/HttpFoundation/compare/cdee7c84ba8b2a8aafa1c055f5cb4f640d81c129...11ad7352c7bfa12145a0df8e1c4c303c585ce169
https://github.com/symfony/HttpKernel/compare/445d6eee0eab2a6cfab41b5dc43f1b86ec34d110...f4e3f0fd1a08c1c4e2ffa044e6910f7ecc7ad317
https://github.com/symfony/Security/compare/ae020b9dc10e6438dc4033103c16bae7d46a4dd6...ef511d47c94ad92e37112b43efcbf7da8696a803
https://github.com/squizlabs/PHP_CodeSniffer/compare/623905ce571d64a8cb873826d47b81321cd55011...339b91cd73c9930c792d54092dc6e1cd376b7a8d
https://github.com/symfony/Yaml/compare/bb6ddaf8956139d1b8c360b4b713ed0138e876b3...77a41c2835ab7cfe8bf6d15e25d3af8f3eb3bacd

Links for new dependencies:
https://github.com/symfony/PropertyAccess
https://github.com/symfony/Translation
https://github.com/symfony/Validator