Raise an error when path is specified with :moved_from or :moved_to

[kenhys]

If same path is specified with :moved_from or :moved_to
additionally, :modify is not fired expectedly.

  require "rb-inotify"
  notifier = INotify::Notifier.new
  notifier.watch("test.log", :modify) do |event|
    puts "#{event} is modified"
  end
  notifier.watch("test.log", :moved_from) do |event|
    puts "#{event} is moved_from"
  end

Above sample code does not work as expected.
So, raise an error immediately.

[coveralls]

Coverage increased (+0.2%) to 80.556% when pulling bf2fc88 on kenhys:error-moved-to-file into 010f140 on guard:master.

[uvlad7]

I'd say it's just one of inotify's pitfalls and it's better to keep ruby wrapper as thin as possible
But if you stil want an check, I'd suggest adding IN_ONLYDIR flag if any of problematic flags are specified, but it still might be a problem for users if they pass the same flags for dirs and files

UPD: inotify doesn't have an 'event only for dirs' type, there are only events that can happen for files in a dir and both for a dir and files inside (note that these differences apply only when monitoring a directory); and

  require "rb-inotify"
  notifier = INotify::Notifier.new
  notifier.watch("test.log", :modify, :moved_from) do |event|
    puts "#{event} is modified"
  end

works fine.
Maybe it's a problem of inotify_add_watch itself?