Update meta.yaml with description and BSD version (#1509)

Summary:
Pull Request resolved: #1509

See title.

Reviewed By: aobo-y

Differential Revision: D69953942

fbshipit-source-id: 373a6b1838f088fb9566895e2e7d276e4bc6a1ee

Author: craymichael

.conda/meta.yaml

@@ -28,8 +28,14 @@ test:
 
 about:
   home: https://captum.ai
-  license: BSD
+  license: BSD-3
   license_file: LICENSE
   summary: Model interpretability for PyTorch
+  description: |
+    Captum is a model interpretability and understanding library for PyTorch.
+    Captum means comprehension in Latin and contains general purpose implementations
+    of integrated gradients, saliency maps, smoothgrad, vargrad and others for
+    PyTorch models. It has quick integration for models built with domain-specific
+    libraries such as torchvision, torchtext, and others.
   doc_url: https://captum.ai
   dev_url: https://github.com/pytorch/captum