Add helper method in Ruby for writing to the logs

[Marak]

Currently there is no easy way to send logging messages from ruby.

It should be easy, just create a log helper method.

Here is some sample lua code to give an idea:

function log(...)
  io.stderr:write('{ "type": "log", "payload": { "entry": ' .. json.stringify(arg, false) .. '}}')
end

log method would probably go here: https://github.com/Stackvana/microcule/blob/master/bin/binaries/micro-ruby#L4