Setting exit code on failure and bug fixes

Bug Fixes 🐛

• Fix reachable check for directories (8f3e812)
• checks: Fixes conditional statement in reachable check (2aaf6c7)
• checks: reachable check should use status of last redirect (5b83f98)
• reachable: parses redirected headers and searches for 200 ok (#80) (35e986d)

Features 💡

• Exit code = 1 when any checks fail (50fb273)