P31
P32
P33
Merge pull request #38 from padilo/arithmetic_week1

Arithmetic week1
Implemented P31 to P33
Merge branch 'master' of github.com:scala-developers-bcn/challenges
Merge pull request #39 from akustik/master

Implemented P31 to P33
Solves P31 (naive impl)
Solves P32
Solves P33
Code cleanup
Merge pull request #40 from ignasi35/master

Arithmetics P31-P33
Solve P21... old homework :-(
Solve P22 and P23. Old homework :-(
Solve P24. Old homework :-(
Merge pull request #41 from ignasi35/master

P21 to P24