Update "iPhone 4 devices" to "unofficial Siri-devices"

Changes all sentences that says something about iPhone 4 to "devices that doesn't come with Siri" and "unoffical Siri devices".
Update typo
Update typo2
fix dns.rb
Merge pull request #476 from jontingvold/patch-1

Update "iPhone 4 devices" to "unofficial Siri-devices"
require rubydns 0.6.0 or greater
add pessimistic version contraint for rubydns
Merge pull request #484 from akston/dns_fix

fix dns.rb