Add resolver to output

[meme-lord]

It would be useful to get the resolver that returned the response in the output. Makes it easier to remove resolvers that are returning bogus responses.

[blechschmidt]

There is an r flag for the simple mode to prepend resolver IP address, Unix timestamp and return code to the question line.

[rkreddypandu]

@blechschmidt , With the "r" flag, massdns is not giving any output. The sample command I used is "massdns -r resolvers.txt -t A domains.txt -o Sr"