Write benchmarking for search functions

[PaMeirelles]

Just the base functionality of measuring the time elapsed in the running of Flop's search function in about ~12 positions. In the future, we can raise additional issues for:

• A new layer of abstraction that allows for testing regardless of evaluation function
• Support for multiple tests in the same positions to improve reliability
• Improve reporting with plotting or comparisons
• Use of positions from real games