Server Side signed requests are failing with any version of request npm package newer than 2.25.0.

This is an example code to verify the bug:

```js
function init() {
	"use strict";

	OAuth.initialize('YOUR_KEY');

	var linkedinButton = document.getElementById('load-linkedin');
	linkedinButton.addEventListener('click', function () {
		OAuth.popup('linkedin', function(err, result) {
			showError(err);
			processLinkedinResult(result);
		});
	});
}

function processLinkedinResult(result) {
	"use strict";

	console.log(result);

	result.get('/v1/people/~').done(function(data) { // this will fail
		processLinkedInData(data);
	});

}

function processLinkedInData(data) {
	"use strict";

	var linkedinInfo = document.getElementById('linkedin-info');
	var firstName = data.evaluate('/person/first-name', data, null, XPathResult.ANY_TYPE, null).iterateNext().textContent;
	var lastName = data.evaluate('/person/last-name', data, null, XPathResult.ANY_TYPE, null).iterateNext().textContent;
	linkedinInfo.innerText = firstName + ' ' + lastName;
	linkedinInfo.textContent = firstName + ' ' + lastName;

}

function showError(err) {
	"use strict";
	if (!!err) {
		for (var key in err.body) {
			alert(key);
		}
	}
}
```

I strongly suggest that this should be added as a test case.