In iOS 7 set forcePickSearchResult to YES cause keyboard never dismissed!

Steps to reproduce:
1. Run TokenFieldExample on iPad(not simulator).
2. Touch the token field and do not input any word.
3. The keyboard popup, but click the "dismiss keyboard button" nothing
happening.
If run on iOS 6, "dismiss keyboard button" just work fine.But on iOS
7,the keyboard does not disappear, it just stays there. The user can
still navigate through back navigation bar button, but all text fields
are disabled, meaning you can't enter text anywhere. The only option
the user has is killing the app and starting fresh.
Try to send resignFirstResponder messages, but no help anything.
This commit fixed it.