Refactor tree structure

[ivanallen]

• binary-tree
  • [x] build tree
  • [x] rotate
  • [x] traversal
  • [x] dump
  • [ ] show
• binary-search-tree
  • [ ] insert
  • [ ] remove #30
  • [x] search
• red-black-tree
  • [x] insert
  • [x] remove

[jovany-wang]

可以给一个简单的design docs吗

[ivanallen]

可以给一个简单的design docs吗

参考 binary-tree/binarytree.h