Refactor src/uri.rl to support RFC3986 and add Lua bindings

 * Split parser and resolver in src/uri.rl
 * Extend URI parser grammar to fully support RFC3986
 * Add Lua bindings to URI parser
 * Implement proper DNS logic in coio_connect() /
   evio_service_bind()
 * Replace uri_to_string() with sio_strfaddr()

Prerequisite for #447