clean introduction placeholder before first time set it

Podfile.lock

@@ -53,7 +53,7 @@ DEPENDENCIES:
 
 EXTERNAL SOURCES:
   MZFayeClient:
-    :path: "../CatchLib-iOS/MZFayeClient/"
+    :path: ../CatchLib-iOS/MZFayeClient/
 
 SPEC CHECKSUMS:
   1PasswordExtension: 9f471645d378283cb88c6d4bf502e4381a42c0ad

Yep/Views/Cells/EditProfileMoreInfo/EditProfileMoreInfoCell.swift

@@ -38,6 +38,16 @@ class EditProfileMoreInfoCell: UITableViewCell {
 
 extension EditProfileMoreInfoCell: UITextViewDelegate {
 
+    func textViewShouldBeginEditing(textView: UITextView) -> Bool {
+
+        // 初次设置前，清空 placeholder
+        if YepUserDefaults.introduction.value == nil {
+            textView.text = ""
+        }
+
+        return true
+    }
+
     func textViewDidChange(textView: UITextView) {
 
         infoTextViewIsDirtyAction?()