Add an option to set a timeout for XHR requests (#95)

Closes #24.

lib/proto/parse-options.js

@@ -23,6 +23,7 @@ module.exports = function(options){
   this.options.scrollTo = (typeof this.options.scrollTo === 'undefined') ? 0 : this.options.scrollTo;
   this.options.cacheBust = (typeof this.options.cacheBust === 'undefined') ? true : this.options.cacheBust
   this.options.debug = this.options.debug || false
+  this.options.timeout = this.options.timeout || 0
 
   // we can’t replace body.outerHTML or head.outerHTML
   // it create a bug where new body or new head are created in the dom
@@ -37,4 +38,4 @@ module.exports = function(options){
   if (typeof options.analytics !== "function") {
     options.analytics = function() {}
   }
-}
+}

lib/request.js

@@ -15,12 +15,17 @@ module.exports = function(location, options, callback) {
     }
   }
 
+  request.ontimeout = function() {
+    callback(null, request)
+  }
+
   // Add a timestamp as part of the query string if cache busting is enabled
   if (this.options.cacheBust) {
     location += (!/[?&]/.test(location) ? "?" : "&") + new Date().getTime()
   }
 
   request.open(requestMethod.toUpperCase(), location, true)
+  request.timeout = options.timeout
   request.setRequestHeader("X-Requested-With", "XMLHttpRequest")
   request.setRequestHeader("X-PJAX", "true")