#21 allow picking of range of numbers - pull request

- added unit tests
- sample outputs :
 - ` {1~5}` results numbers from 1 to 5
 - `{1~5|abc|efg|10~12}` results to numbers from 1 to 5 or `abc` or `efg`
or numbers 10 to 12
 - `{test~ing|some}` results to `test~ing` or `some`