ENH: Adding Google Colab Support (#115)

* added colab url

* reverting to quantecon

Author: AakashGfude

lectures/_config.yml

@@ -68,6 +68,8 @@ sphinx:
       description: This website presents a set of lectures on advanced quantitative economic modeling, designed and written by Thomas J. Sargent and John Stachurski.
       keywords: Python, QuantEcon, Quantitative Economics, Economics, Sloan, Alfred P. Sloan Foundation, Tom J. Sargent, John Stachurski
       google_analytics_id: UA-54984338-11
+      launch_buttons:
+        colab_url             : https://colab.research.google.com
     mathjax3_config:
       tex:
         macros: