Fix Q1.3 python solution

s2.replace was ineffective, reassign s2 to result from replace
Create Chapter3Solution.scala

solutions of chapter 3
Merge pull request #66 from yrbahn/master

Chapter3Solution.scala
Solutions of chapter 4 (4.1 ~ 4.7)
Update Chapter4Solution.scala
Merge pull request #67 from yrbahn/master

scala solutions of chapter 4
Merge pull request #64 from mriddle/mr-fix-python-chapter-1-question-1-3

Fix Q1.3 python solution
Chapter 3 for C++
Merge pull request #71 from sarvesh-onlyme/master

Chapter 3 for C++
Chapter 4 for C++
Merge pull request #72 from sarvesh-onlyme/master

Chapter 4 for C++
Implemented Swift solutions for Chapter 1
Update ChapQ1.5.py
Merge pull request #73 from caferyil/patch-1

Update ChapQ1.5.py
Update Question2_7.py
Update ChapQ4.5.py
Merge pull request #77 from caferyil/patch-4

Update ChapQ4.5.py
Update ChapQ4.6.py
Update BinaryTreeNode.py
Update ChapQ4.8.py