Remove .md and image files and move python files into main chapter folders

thinkcspy/Chapter-8-Exercises/Problem3.py

@@ -0,0 +1,13 @@
+# Runestone.Academy thinkcspy course
+# Chapter 8
+# Problem 3
+
+def is_prime(n):
+    # your code 
+        
+    for i in range (2, n):
+        if n % i == 0:
+            return False
+    return True
+
+print(is_prime(25))