added optional start parameter, enabling pagination

lib/google.js

@@ -12,8 +12,15 @@ var URL = 'http://www.google.%s/search?hl=%s&q=%s&start=%s&sa=N&num=%s&ie=UTF-8&
 
 var nextTextErrorMsg = 'Translate `google.nextText` option to selected language to detect next results link.'
 
-function google (query, callback) {
-  igoogle(query, 0, callback)
+// start parameter is optional
+function google (query, start, callback) {
+  var startIndex = 0
+  if (typeof callback === 'undefined') {
+    callback = start
+  } else {
+    startIndex = start
+  }
+  igoogle(query, startIndex, callback)
 }
 
 google.resultsPerPage = 10

test/google.test.js

@@ -132,4 +132,25 @@ describe('+ google()', function () {
 
     })
   })
+
+  describe('when start is set', function () {
+    it('optional start parameter should return search results', function (done) {
+      var allLinks = []
+      var query = 'Microsoft'
+      var timeFrame = 'm'
+
+      var finished = function () {
+        assert(allLinks.length === 10)
+        done()
+      }
+
+      google.resultsPerPage = 10
+      google.timeSpan = timeFrame
+      google(query, 2, function (err, next, links) {
+        assert.ifError(err)
+        allLinks = allLinks.concat(links)
+        finished()
+      })
+    })
+  })
 })