Add parsing for torch nightlies/dev back in

Note that this does currenlty not work properly on pip 19.0.1 due to a bug: pypa/pip#6163

Author: Balandat

setup.py

@@ -28,6 +28,17 @@ def find_version(*file_paths):
 version = find_version("gpytorch", "__init__.py")
 
 
+torch_min = "1.0.1"
+install_requires = [">=".join(["torch", torch_min])]
+# if recent dev version of PyTorch is installed, no need to install stable
+try:
+    import torch
+    if torch.__version__ >= torch_min:
+        install_requires = []
+except ImportError:
+    pass
+
+
 # Run the setup
 setup(
     name="gpytorch",
@@ -45,7 +56,7 @@ def find_version(*file_paths):
     classifiers=["Development Status :: 4 - Beta", "Programming Language :: Python :: 3"],
     packages=find_packages(),
     python_requires=">=3.6",
-    install_requires=["torch>=1.0.1"],
+    install_requires=install_requires,
     extras_require={
         "dev": [
             "black",