chore(project): update .gitignore for .idea directory
chore(project): defines sub-projects
 - complex : complex API
 - matrix : matrix API
chore(project): defines rational sub-project
 - rational : a rational number api
feat(complex): first complex implementation
feat(rational): first rational implementation
chore(project): defines root project
feat(complex): tranform Complex to a case class
feat(rational): transform Rational to a case class