added tests for utils.py at tests/test_utils.py also changed a keyword argument from headers to user_agent for latest_version of utils.py with the usual default vaule.

waybackpy/utils.py

@@ -4,8 +4,9 @@ from .__version__ import __version__
 DEFAULT_USER_AGENT = "waybackpy %s - https://github.com/akamhy/waybackpy" % __version__
 
 
-def latest_version(package_name, headers):
+def latest_version(package_name, user_agent=DEFAULT_USER_AGENT):
     request_url = "https://pypi.org/pypi/" + package_name + "/json"
+    headers = {"User-Agent": user_agent}
     response = requests.get(request_url, headers=headers)
     data = response.json()
     return data["info"]["version"]