Add leap exercise
Add series exerice
Add robot-simulator exercise
Add parallel_letter_frequency exercise
Merge pull request #14 from ebengt/leap

Add leap exercise
Merge pull request #16 from ebengt/series

Add series exerice
Merge pull request #17 from ebengt/robot-simulator

Add robot-simulator exercise
Merge pull request #19 from ebengt/parallel-letter-frequency

Add parallel_letter_frequency exercise