removed original s6_2 definition and replaced characteristicsSpecification in s6_intro
removed original s6_2 definition and replaced characteristicsSpecification in s6_intro

JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software