Update docs.md (#461)

I think top should be equal to safeAreaLayoutguide.snp.top

docs.md

@@ -341,7 +341,7 @@ class MyViewController: UIVewController {
 
         self.view.addSubview(tableView)
         tableView.snp.makeConstraints { (make) -> Void in
-           make.top.equalTo(self.safeAreaLayoutGuide.snp.bottom)
+           make.top.equalTo(self.safeAreaLayoutGuide.snp.top)
         }
     }
 
@@ -350,4 +350,4 @@ class MyViewController: UIVewController {
 
 <br/>
 <br/>
-<br/>
+<br/>