Print error if dnssd library not available
Some clarifications in the README.md
Add installation and usage instructions
Make shairplay not exit after 100 seconds
Add signal handlers to shairplay to make it shut down gracefully
Add supported flags to the README
Remove dnssd_register_airplay that was accidentally added
Revert "dns_sd check during configure for linux"

This reverts commit e6dca0a28ecee7eac3c62b9a8c1fa6e668c55c02.
Merge branch 'master' of https://github.com/juhovh/shairplay
Changed library name for libdns_sd search, added error info