update binder link

[mikofski]

I updated the link and reworded this section:

-      
-      
-      ## Tutorial Setup
-      
-      This tutorial is designed to run on [Binder](https://mybinder.org/). This will
-      allow you to run the tutorial in the cloud without any additional setup. To get
-      started, simply click
-      
-      [here](https://mybinder.org/v2/gh/xarray-contrib/xarray-tutorial/master?urlpath=lab):
-      [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/xarray-contrib/xarray-tutorial/master)
-      
+      This tutorial is designed to run on [Jupyter](https://jupyter.org), an online interactive notebook that allows you to run the
+      tutorial in the cloud without any additional setup. During the conference, June 20-25, you will be provided with a link and
+      credentials to join the tutorial. After the conference the tutorials will remain available on
+      [GitHub](https://github.com/mikofski/PVSC48-Python-Tutorial), and you can run them interactively using
+      [Binder](https://mybinder.org/) by clicking the link below:
+      
+      [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/mikofski/PVSC48-Python-Tutorial/master?filepath=Tutorial%200%20-%20Overview.ipynb)

[mikofski]

Finally! It works! I moved it to the README, b/c (1) i've found it doesn't work as well from inside a jupyter notebook, and (2) it's redundant, once you're in the notebook why would want the link? When you visit the GH site, the first thing you see is the readme, so that's where I put the binder link.

Also I updated the run locally instructions to use the requirements.txt and put it in the context of miniconda. I tested the environment and it works.

Anyone, if you're ok with changes, feel free to merge this whenever. Doesn't depend on anything