Update README.md

Sample updated to SDK v3.5.1

Merge pull request #9 from hypertrack/bug/rename-custom-events-into-t…

…rip-markers

Bug/rename custom events into trip markers

SDK version updated

Releases/v3.1.0 (#1)

* New simplified SDK interface
* Custom events support
* Switched to AndroidX support library flavor
* library ProGuard file was added
* Bug fixes

Version 3.0.0 sdk (#2)

Update build.gradle