Update doctest
Rewrite __repr__ change print to str
Create method set_percent_problems_solved_by_time

This solve #17.

The method set_percent_problems_solved_by_time of prof.Pdata
replace generate_perf_functions of tikz.Profiler.

matplotlib.Profiler now use set_percent_problems_solved_by_time.
Add --raw option and required group for parser
Merge pull request #19 from r-gaia-cs/repr

Rewrite __repr__ change print to str
Merge remote-tracking branch 'raniere/profile' into repr
Merge branch 'repr'
Merge remote-tracking branch 'origin/master'