README: Make a link to wiki of TizenRT github
The link to wiki provides what TizenRT is and How to use it.
[![Build Status](https://travis-ci.org/Samsung/TizenRT.svg?branch=master)](https://travis-ci.org/Samsung/TizenRT)
lightweight RTOS-based platform to support low-end IoT devices.
-Please find project details like APIs reference at [docs](docs/) folder. Wiki will be provided.
+Please find project details at [Wiki](https://github.com/Samsung/TizenRT/wiki) especially [documentations page](https://github.com/Samsung/TizenRT/wiki/Documentations).
## Contents
