Ensure getResponseHeader is case insensitive

[gasi]

First of all, thanks for all the great work in XHook and XDomain 😄 I am using it with superagent and ran into a bug where superagent can’t automatically decode the response body because the response content-type is undefined. I tracked it down to a small bug in XHook as outlined below.

The getResponseHeader method should not treat headers as case sensitive. I’d suggest [normalizing, e.g. lowercasing, all response headers](:

xhook/src/xhook.coffee

Lines 121 to 134 in bb38b1e

	convertHeaders = xhook.headers = (h, dest = {}) ->
	switch typeof h
	when "object"
	headers = []
	for k,v of h
	headers.push "#{k}:\t#{v}"
	return headers.join '\n'
	when "string"
	headers = h.split '\n'
	for header in headers
	if /([^:]+):\s*(.+)/.test(header)
	dest[RegExp.$1] = RegExp.$2 if not dest[RegExp.$1]
	return dest
	return

) before storing them in headers.

W3C compatibility tests: https://github.com/w3c/web-platform-tests/blob/master/XMLHttpRequest/getresponseheader-case-insensitive.htm

Let me know if you need any more info and have a great day!

[jpillora]

ah yep thanks - definitely a bug - will fix when i can

[gasi]

Never mind, let me give it a shot 😄

[gasi]

Pull request: #17