Remove need to store if converged and store times

After parsing, the converged status is implied by the measure used.
If the algorithm does not converge, the value is inf.
Merge remote-tracking branch 'abel/times' into HEAD
Basic matplotlib generator

* Add very basic matplotlib generator
* Update main function
* Update installation instructions

List of EASY things to be done:

* Add option to output file name
* Add options of output (e.g. pdf, ps, eps and svg)

List of others things to be done:

* Add legend
* Add axis names
* Add title