Add Node 4.0.0 support
Add Node 4.0.0 support

johansten/js-stellar-base,strllar/js-stellar-base,stellar/js-stellar-base,stellar/js-stellar-base,strllar/js-stellar-base,manran/js-stellar-base,strllar/js-stellar-base,johansten/js-stellar-base,manran/js-stellar-base,manran/js-stellar-base,johansten/js-stellar-base