Support "2-digit" month format

[r1b]

In Chrome 43.0.2357.132 I see:

new Intl.DateTimeFormat('en', {
     month: '2-digit'
}).format(Date.now());
"07"

In node v0.10.38 with latest Intl in npm I see:

new Intl.DateTimeFormat('en', {
     month: '2-digit'
}).format(Date.now());
"7"

[caridy]

Fixed by PR #146, shipped in intl@1.1.0