Update README and test script

Author: RussellDash332

README.md

@@ -19,6 +19,7 @@ Construct a `Kattis` object that takes in the username and the password.
 ```py
 from autokattis import Kattis
 kt = Kattis('username', 'password')
+kt = Kattis('username') # which will then prompts you for the password
 ```
 
 where `'username'` is your Kattis username/email and `'password'` is your Kattis account password. **Both should be provided as Python strings.**
@@ -60,6 +61,15 @@ kt.ranklist(university='National University of Singapore')  # university leaderb
 kt.ranklist(university='nus.edu.sg')                        # use university domain instead
 ```
 
+### Convert to DataFrame
+
+As simple as this!
+
+```py
+kt.problems().to_df()
+kt.ranklist().to_df()
+```
+
 ## Useful References
 
 - Old UI Kattis API wrapper: https://github.com/terror/kattis-api

test/main.py

@@ -1,5 +1,3 @@
-import pandas as pd
-
 from autokattis import Kattis
 from env import USER, PASSWORD
 
@@ -32,4 +30,4 @@
     kt.ranklist(university='nus.edu.sg')                        # use university domain instead
 ]:
     if ret:
-        print(pd.DataFrame(ret))
+        print(ret.to_df())