Adding thresholds to diff_pos_max metric
Changes DIF_POS_MAX metric and adapt tests to it
Adapt vignette and manuel to modified code
Change in the prerequisite of the similarity function. Modification of function description.
Activating the example section of Similarity manual
Updating description
Modifying tolerance threshold to be between 0 and 1.
MetricFactory now visible
Correct wrong argument default value.
Merge pull request #2 from adeschen/diffPosMax_modification

Diff pos max modification