Add java solution for 6. ZigZag Conversion
Add java solution for 6. ZigZag Conversion

6. ZigZag Conversion: https://leetcode.com/problems/zigzag-conversion/
ckclark/leetcode,ckclark/leetcode,ckclark/leetcode,ckclark/leetcode,ckclark/leetcode,ckclark/leetcode