Fix 2 bugs appeared in iOS7: Not scrolling properly & Dismiss keyboard not working with UITextView

## Not scrolling properly
View hierarchy of UITableViewCell is different in iOS7.
Apple added `UITableViewCellScrollView` between `UITableViewCellContentView` and `UITableViewCell`, so we should add one more `[view superview]` to get the `UITableViewCell` which `activeField` belongs to.
    
## Dismiss keyboard not working with UITextView
`resignFirstResponder` doesn't work with `UITextView` to dismiss keyboard in iOS7, replace it with `[view endEditing:YES]` to fix it.