system benchmark & system tracer (issue #2, #3)

This version introduces multiple enhancements:

added base logic to Benchmark and Tracer libraries
some examples and readme update

Details of additions/deletions below:
--------------------------------------------------------------

Modified:   Debug/Tracer.php
            -- Added --
                whole library logic

Modified:   README.md
            -- Added --
                documentation links

Modified:   Performance/Benchmark.php
            -- Added --
                whole library logic

Modified:   examples/benchmark.php
            -- Added --
                some examples for Benchmark library