Update README.md Install Steps (#198)

Fixes #195

Author: mikemhenry

README.md

@@ -22,10 +22,22 @@ We show that this approach is not only sufficiently expressive to reproduce lega
 
 # Installation
 
+We recommend using [`mamba`](https://mamba.readthedocs.io/en/latest/mamba-installation.html#mamba-installation) which is a drop-in replacement for `conda` and is much faster.   
+
+```bash
+$ mamba create --name espaloma -c conda-forge "espaloma=0.3.2"
+```
+
+Note: If you are using a Mac with a M1/M2 chip, you will need to install and run `espaloma` using [Rosetta](https://support.apple.com/en-au/HT211861) by using the following commands:
+
 ```bash
-$ conda install -c conda-forge "espaloma=0.3.2"
+CONDA_SUBDIR=osx-64 mamba create --name espaloma -c conda-forge "espaloma=0.3.2"
+mamba activate espaloma
+mamba config --env --set subdir osx-64
 ```
 
+This will ensure that any other packages installed in the `espaloma` will also use Rosetta.
+
 # Example: Deploy espaloma 0.3.2 pretrained force field to arbitrary MM system
 
 ```python