use mamba to install rmg

Author: JacksonBurns

.github/workflows/CI.yml

@@ -4,8 +4,6 @@ on:
     branches:
       - main
   push:
-    branches:
-      - main
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -29,6 +27,9 @@ jobs:
           environment-file: environment.yml
           python-version: 3.7
           activate-environment: rms_env
+	  miniforge-variant: Mambaforge
+	  miniforge-version: latest
+	  use-mamba: true
       - name: Fix PyCall linking
         run: |
             julia -e 'ENV["PYTHON"]=ENV["CONDA"] * "/envs/rms_env/bin/python"; using Pkg; Pkg.add("PyCall"); Pkg.build("PyCall")'