Remove composer.lock from repo for now

This change needs to be discussed properly and a unified approach needs to
be decided upon for all of the Alert-based project family. I'm doing it
for now to make Travis builds useful.

/cc @Danack @rdlowrey
Convert Resolver to unified interface
Implement OrderedResolverStrategy properly
Improve IP literal resolution resiliency

Allow [xxx] syntax for IPv6 addresses, to facilitate usage with directly parsed URI components