Android BLE Library v 2.5.1

What's Changed

• Dependencies updated by @philips77 in #394
• Keep onConnectionUpdated method from being removed by proguard by @philips77 in #395
• Null checks for service discovery by @philips77 in #396
• Readme fixed by @philips77 in #397

Full Changelog: 2.5.0...2.5.1