Implement BTree indexer

[0xnullifier]

Btree are important data structures they occur in modified form almost everywhere from databases to the file system.

A Btree based indexer should allows for the following

• Efficient O(log n) operations including insertion deletion and traversal.
• Range query support
• Thread-Safety
• Proper tree balancing

You are allowed to use the Btree implementation already packaged internally for the Indexer. The scoring for using library will be a MEDIUM while a full implementation including implementing the BTree yourself will be awarded points for a HARD problem.