Add absolute position plotting
Fork a process for each timeit!

* Separate the environment for each timeit, this may use more
  system ressource but it has fixed the bug!
Delete useless curves on plotting

* worst, mean, median...
Fix bug of the default commits.

* If no commit selected, the script choose all the commits of the given branch
* If no branch selected, the script choose the master.
Create README.md
Add benchmarks

* nqueens
* int_sum
* float_sum