modified to fix the iOS 7.0 compatibility issue

Since the isConnected method has been deprecated in iOS 7.0, replaced
with the state property

https://developer.apple.com/library/ios/documentation/CoreBluetooth/Refe
rence/CBPeripheral_Class/DeprecationAppendix/AppendixADeprecatedAPI.html
update changelog
Fix issue #7
https://github.com/YUKAI/konashi-ios-sdk/issues/7
Separating UI code from logic code.