XML parser should raise when encountering errors.

[justfalter]

Right now, it just stops parsing and does not raise any exceptions.

This example does not raise any exceptions, and the block is never executed.

pattern = Threatinator::Parsers::XML::Pattern.new('/foo')
parser = Threatinator::Parsers::XML::Parser.new(pattern: pattern)
sio = StringIO.new("<foo><bar></foo>")
parser.run(sio) do |record|
   puts "never gets run"
end