add model Skill.
add rake task db:populate.
this task inserts required records to db from doc/data.xlsx.
add model NormalSpread.
add model TriangleSpread.
add relation to NormalSpread and TriangleSpread model class.
add model Persona.
add model PersonaSkill.
rename Persona model column special_spread to dlc_content.
add model SpecialSpread.
move data.xlsx to rake tasks directory.