Revamp the speed comparison test.

Focus on parsing with location tracking.
Use the upstream code for the parsers.

https://code.google.com/p/esprima/issues/detail?id=424
Always benchmark with location tracking parsing.

https://code.google.com/p/esprima/issues/detail?id=424
For the benchmark result, show relative mean error instead of variance.

https://code.google.com/p/esprima/issues/detail?id=424
Speed comparison: No need to display the source size.

We need the precious horizontal space.

https://code.google.com/p/esprima/issues/detail?id=424