Updating to use pipenv instead of requirements.txt

Author: jmeulemans

Pipfile

@@ -14,6 +14,10 @@ pyorient = "==1.5.5"
 pytest = "==4.0.2"
 pytest-cov = "==2.5.1"
 snapshottest = "==0.5.0"
+cython = "==0.29.2"
+mysqlclient = "==1.3.14"
+"psycopg2" = "==2.7.5"
+pymssql = "==2.1.4"
 
 [packages]
 arrow = "==0.10.0"