Fix decaffeinate in iojs v1.6.x.
Fix decaffeinate in iojs v1.6.x.

It seems iojs removed the ability to specify only the encoding, so now
we just have to pass the encoding as the value of the "encoding" option
in an object.

Closes #21.

decaffeinate/decaffeinate,netei/decaffeinate,lunks/decaffeinate,greyhwndz/decaffeinate,netei/decaffeinate,alangpierce/decaffeinate,lunks/decaffeinate,eventualbuddha/decaffeinate,edi9999/decaffeinate,eventualbuddha/decaffeinate,alangpierce/decaffeinate,decaffeinate/decaffeinate,alangpierce/decaffeinate