added pandas to requirements file

requirements.txt

 Brotli==1.0.9
+certifi==2020.12.5
 click==7.1.2
 dash==1.19.0
 dash-core-components==1.15.0
@@ -15,7 +16,10 @@ itsdangerous==1.1.0
 Jinja2==2.11.3
 MarkupSafe==1.1.1
 numpy==1.20.1
+pandas==1.2.4
 plotly==4.14.3
+python-dateutil==2.8.1
+pytz==2021.1
 retrying==1.3.3
 scipy==1.6.1
 six==1.15.0