Add Chapter 6 python files and fix grammar issues in readme

thinkcspy/Chapter-6-Exercises/Python-files/problem14.py

@@ -0,0 +1,14 @@
+# Runestone.Academy thinkcspy course
+# Chapter 6
+# Problem 14
+
+def mySqrt(n):
+    # your code here
+    oldGuess = n/2
+    
+    while oldGuess**2 != n:
+        oldGuess = (1/2)*(oldGuess+(n/oldGuess))
+    
+    return oldGuess
+    
+print(mySqrt(10000))