Revert "Calculate scroll view frame correctly (#72)"

This reverts commit 5d30ee4.

Author: rnystrom

MessageViewController/MessageViewController.swift

@@ -126,12 +126,11 @@ open class MessageViewController: UIViewController, MessageAutocompleteControlle
         // required for the nested UITextView to layout its internals correctly
         messageView.layoutIfNeeded()
 
-        let frame = scrollView.frame
         scrollView.frame = CGRect(
-            x: frame.minX,
-            y: frame.minY,
-            width: frame.width,
-            height: messageViewFrame.minY - frame.minY
+            x: bounds.minX,
+            y: bounds.minY,
+            width: bounds.width,
+            height: messageViewFrame.minY
         )
 
         messageAutocompleteController.layout(in: view, bottomY: messageViewFrame.minY)