Updated the option to get number to words

Updated the option to get number to words.
python dependency needed: https://pypi.python.org/pypi/num2words

Usage:
<t t-esc="XXXX" t-esc-options='{"widget": "num2words","case":"upper"}'/> or
<t t-esc="o.amount_total" t-esc-options='{"widget": "num2words"}'/>