Library incorrectly uses case sensitive MDNS host name matching

[matthewgream]

To reproduce:

• configure ArduinoMDNS with a snakecase name, e.g. "ThisHost"
• enter "thishost.local" into browser
• observe no name resolution
• reconfigure ArduinoMDNS with a lowercase name, "thishost"
• enter "thishost.local" into browser
• observe name resolution