add useful links to readme
# Pixel [![GoDoc](https://godoc.org/github.com/faiface/pixel?status.svg)](https://godoc.org/github.com/faiface/pixel) [![Go Report Card](https://goreportcard.com/badge/github.com/faiface/pixel)](https://goreportcard.com/report/github.com/faiface/pixel)
A 2D game library that doesn't get in your way. Focus on ease of use, extensibility and performance.
+Take a look into the [features](#features) to see what it can do.
```
go get github.com/faiface/pixel
```
+See [requirements](#requirements) for the list of libraries necessary for compilation.
+
## Tutorial
The [Wiki of this repo](https://github.com/faiface/pixel/wiki) contains an extensive tutorial
