Added pyyaml package to Pipfile (#95)

Encountered an issue using `pipenv` after installing the
packages associated with the project for a missing package.

Author: selpan

Pipfile

@@ -45,6 +45,7 @@ python-dateutil = "*"
 setuptools = "*"
 urllib3 = "*"
 cookiecutter = "*"
+pyyaml = "*"
 
 [requires]
 python_version = "3.7"