fixed hardcoded Symfony 4 requirement

also improved Symfony 4 compatibility.

2.6.0

• 3521f6e Symfony4 compatibility fixes (Lukas Kahwe Smith)
• 19c1571 ensure we have symfony4 compatible deps (Lukas Kahwe Smith)
• 2c789c4 adding especial for 4.0 (Luis Cordova)
• 870a06b adding travis (Luis Cordova)
• bbc7bd4 we move to 4.0 constraints (Luis Cordova)
• a793399 Added support for tag autoconfiguration (Iltar van der Berg)
• 13bd269 Change on travis configuration to validate test (Hugues Gobet)
• bb5eaf7 Change configuration to adapt it to my new check (dist:trusty) (Hugues Gobet)
• 167254a Change configuration to adapt it to my new check (Hugues Gobet)
• 357cfdb Adding a check for mongodb connection (Hugues Gobet)
• d01f68a Removed extra param escaping where we need the value pushed (thanosp)

2.5.2

• 255f7a5 Added workaround for undefined services of symfony3 (#145) (Thanos Polymeneas)

2.5.1

• 77b1e22 Fix : dummy query instead of hard query (LandryBe)

2.5.0

• 15190bc Change minimum PHP version to 5.4 (Evgenij Efimov)
• 649a7aa Added doctrine migrations check (Evgenij Efimov)
• 9c03234 updated build matrix, increase memory limit (Lukas Kahwe Smith)

2.4.1

• f531962 allowing sensiolabs/security-checker v4 (Guilherme Donato)

2.4.0

• 8992b1c Fix CS issue and array syntax (zumba)
• fb9571f Verify PDOCheck class exists when using pdo_connections check (zumba)
• 2b62bde PDO Connections check implementation (zumba)
• 19faef2 switch from guzzle/guzzle to guzzlehttp/guzzle in development (Kevin Bond)
• 3f7820a add Symfony 3.1 to travis test matrix (Kevin Bond)

2.3.4

• 0d91668 switch from deprecated CommandEvent to Event (Kevin Bond)

Fixed BC for missing method in sf ^3.0

see d5175eb

Added Redis password support

• 42b807b Added Redis password support (Igor Timoshenko)