downgrade some deps for py36 compat

Author: rodluger

environment.yml

@@ -4,7 +4,7 @@ channels:
   - conda-forge
 dependencies:
   - python=3.8
-  - numpy>=1.19.4
+  - numpy>=1.19.2
   - pip>=20.3.3
   - scipy>=1.5.2
   - setuptools>=51.3.3
@@ -14,8 +14,8 @@ dependencies:
   - nb_conda_kernels
   - nb_anacondacloud
   - pip:
-    - astropy>=4.2.1
-    - matplotlib>=3.4.2
+    - astropy>=4.1.0
+    - matplotlib>=3.3.4
     - nose>=1.3.7
     - parameterized>=0.8.1
     - pytest>=6.2.4

setup.py

@@ -21,9 +21,9 @@
     },
     install_requires=[
         "setuptools_scm",
-        "numpy>=1.19.4",
-        "matplotlib>=3.4.2",
-        "astropy>=4.2.1",
+        "numpy>=1.19.2",
+        "matplotlib>=3.3.4",
+        "astropy>=4.1",
         "vplanet>=2.0.0",
     ],
     entry_points={