Fixing broken link to documentation

Author: pvnbhargava

README.md

@@ -1,5 +1,5 @@
 # ACG
 Arbitrary Cell Generator is a plugin to Berkeley Analog Generator 2.0 (BAG) that enables parametrized
-grid-free layout creation. Documentation can be found at <acg.readthedocs.io>
+grid-free layout creation. Documentation can be found at <https://acg.readthedocs.io>
 
 NOTE: ACG is currently in development, and is being slowly cleaned up for open-source consumption, use at your own risk!