Inconsistent behavior when parsing spelled out numbers (ranges)

[Yoav Goldberg]

Describe the bug
parser.parse("between 5 and 6") returns 5.5 with uncertainty 0.5
while
parser.parse("between five and six") returns 11

Expected behavior
parser.parse("between five and six") should return 5.5 with uncertainty 0.5

[Yoav Goldberg]

fixed by #203