Logging

[haoliangyu]

When the CLI tool runs, it should print out the log messages for each file, suite, and case. The format should look like

/my-project/benchmarks/search.js

  search
    * by id x 4,161,532 +-0.99% (59 cycles)
    * by name x 4,231,578 +-0.89% (56 cycles)

  search-string
    * by org x 5,234,786 +-0.95% (73 cycles)

The logging logic should be wrapped into a Logger class.