should send request with ACCEPT headers when load xml from remote

[khiav223577]

In rails server, when a request has no ACCEPT field in the HEADER, it will regard it as html format (ref)

Since we are going to load the xml from remote, it would be better if we can setup the correct headers for server to determine which format should be responded.

Related code

wasabi/lib/wasabi/resolver.rb

Lines 43 to 50 in b2abe78

	def load_from_remote
	request.url = document
	response = HTTPI.get(request, adapter)
	raise HTTPError.new("Error: #{response.code} for url #{request.url}", response) if response.error?
	response.body
	end

Possible code to setup the header

request.headers['ACCEPT'] = 'application/xml'