resolver_ares.py:
- gethostbyname now handles '' (empty string)
- getaddrinfo now handles integer ports of type string, e.g "25". Thanks to kconor.
- getaddrinfo now converts UnicodeEncodeError into error('Int or String expected')
- getaddrinfo now uses the lowest 16 bits of passed port integer, to mimic socketmodule.c
- getnameinfo calls getaddrinfo to process arguments, similar to socketmodule.c
- gethostbyaddr also uses getaddrinfo to process arguments

ares.pyx:
- added InvalidIP exception
- gethostbyaddr and getnameinfo now raise InvalidIP immediatelly instead of passing it through callback

"kill" is available as a deprecated alias

convert signal() into a class; the usage did not change; added property 'ref' that is forwarded to watcher

add "ref" argument and property to all watchers; setting it to False makes watcher call ev_unref appropriatelly

removed _incref member
added _flags member

since /usr/bin/python might not be available universally