* Lower_Bound: proved with GNATProve GPL2014, one sucpicious
          invariant to be investigated
        * Added implementation of upper_bound (fully proved)

        * For progressive_split mode, required for chap5 files
        * Minor adjusts to prove, update reference output
        * Implement proposition from D. Mentré on return parameter of
          Argument
        * Ignore more files
Minor formatting
        * Added first draft for chapter 7, to be refined
        * Work on stack type
        * Minor reformatting
        * First try at implementation of bubble sort
        * More files to be ignored
        * Iteration on bubble sort
	* Complete proof of the Bubble Sort
	* Adjust targets to give more time for proving
          SPARK.Bubble_Sort
	* Added reference output for GNATProve GPL2014
        * Enhance distclean target
        * Add SPARK2014 version of Merseen Twister (MT19937) random
          generator
        * Added some comments
        * Complete chapter 5 examples
        * Update output with information on statistics