added implementation of Hamming numbers (ported from scala)
small refactoring + added Hamming numbers to README
corrected range (was printing the first 19 numbers instead of 20)
corrected range (was printing the first 19 numbers instead of 20). use range_inclusive
changed from range_inclusive to range to fight unused import warning
commented code
Merge pull request #113 from pfalabella/hamming_numbers_impl

added implementation of Hamming numbers (ported from scala)