update logo in readme
<div align="center">
- <img src="https://app.wandb.ai/logo.svg" width="350" /><br><br>
+ <img src="https://i.imgur.com/RUtiVzH.png" width="600" /><br><br>
</div>
# Weights and Biases [![ci](https://circleci.com/gh/wandb/client.svg?style=svg)](https://circleci.com/gh/wandb/client) [![pypi](https://img.shields.io/pypi/v/wandb.svg)](https://pypi.python.org/pypi/wandb)
