spells out number names up to 199
spells out number names up to 299
spells out number names up to 999
refactored spell_out/1 clauses for number 10 to 100 and 100 to 1000. Now it is easier to see the pattern
Added tests for numbers up to 2000 and refactored get_lower_limit function and removed number intervals.
Added tests for numbers until a million
refactored get_lower_{ten,hundred,thousand}_limit/1 and transformed into one get_lower_base_limit/2
removed forgotten commented out code
Change in requirements; A comma is needed after thousand ie; a thousand, two hundred and one
Removed defined constant since they are used only once and reveals intention good enough