Added SG phone number support

[SG country code](http://en.wikipedia.org/wiki/Telephone_numbers_in_Singapore#Numbering_plan) are 653, 656, 658, 659
US area code consist of [650](http://www.bennetyee.org/ucsd-pages/area.html#650), [651](http://www.bennetyee.org/ucsd-pages/area.html#651) and [657](http://www.bennetyee.org/ucsd-pages/area.html#657)