change citation to arxiv paper and fix video in readme

Summary: Github does not support embedding youtube videos! Changing it to a link with a thumbnail.

Reviewed By: gkioxari

Differential Revision: D22601430

fbshipit-source-id: 1087657bc379a228a33eced1bee8492cef8373a7

README.md

@@ -53,12 +53,11 @@ We also have deep dive notes on several API components:
 - [Mesh IO](https://github.com/facebookresearch/pytorch3d/tree/master/docs/notes/meshes_io.md)
 - [Differentiable Rendering](https://github.com/facebookresearch/pytorch3d/tree/master/docs/notes/renderer_getting_started.md)
 
-## Overview Video
+### Overview Video
 
-This 14 min tutorial provides an overview of the structure of the PyTorch3D codebase and how to get started including several code examples.
-
-<iframe width="560" height="315" src="https://www.youtube.com/embed/Pph1r-x9nyY" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+We have created a short (~14 min) video tutorial providing an overview of the PyTorch3D codebase including several code examples. Click on the image below to watch the video on YouTube:
 
+<a href="http://www.youtube.com/watch?v=Pph1r-x9nyY"><img src="http://img.youtube.com/vi/Pph1r-x9nyY/0.jpg" height="225" ></a>
 
 ## Development
 
@@ -70,15 +69,15 @@ PyTorch3D is written and maintained by the Facebook AI Research Computer Vision
 
 ## Citation
 
-If you find PyTorch3D useful in your research, please cite:
+If you find PyTorch3D useful in your research, please cite our tech report:
 
 ```bibtex
-@misc{ravi2020pytorch3d,
-  author =       {Nikhila Ravi and Jeremy Reizenstein and David Novotny and Taylor Gordon
+@article{ravi2020pytorch3d,
+    author = {Nikhila Ravi and Jeremy Reizenstein and David Novotny and Taylor Gordon
                   and Wan-Yen Lo and Justin Johnson and Georgia Gkioxari},
-  title =        {PyTorch3D},
-  howpublished = {\url{https://github.com/facebookresearch/pytorch3d}},
-  year =         {2020}
+    title = {Accelerating 3D Deep Learning with PyTorch3D},
+    journal = {arXiv:2007.08501},
+    year = {2020},
 }
 ```
 
@@ -86,6 +85,8 @@ If you find PyTorch3D useful in your research, please cite:
 
 Please see below for a timeline of the codebase updates in reverse chronological order. We are sharing updates on the releases as well as research projects which are built with PyTorch3D. The changelogs for the releases are available under [`Releases`](https://github.com/facebookresearch/pytorch3d/releases),  and the builds can be installed using `conda` as per the instructions in [INSTALL.md](INSTALL.md).
 
+**[July 17th 2020]:**   PyTorch3D tech report published on ArXiv: https://arxiv.org/abs/2007.08501
+
 **[April 24th 2020]:**   PyTorch3D v0.2 released
 
 **[March 25th 2020]:**   [SynSin](https://arxiv.org/abs/1912.08804) codebase released using PyTorch3D: https://github.com/facebookresearch/synsin