Update HDPrivateKey docs. Fixes #1209
Update HDPrivateKey docs. Fixes #1209

martindale/bitcore,phplaboratory/bitcore,genecyber/bitcore,janko33bd/bitcore,bitpay/bitcore,initaldk/bitcore,braydonf/bitcore,eordano/bitcore,bitjson/bitcore,bankonme/bitcore,bitjson/bitcore,iobond/bitcore,lekkas/bitcore,eXcomm/bitcore,iobond/bitcore,TeamPiggyCoin/PiggyCore,pnagurny/bitcore,jcvernaleo/bitcore,eXcomm/bitcore,daxxog/clamcore,phplaboratory/bitcore,williamcotton/bitcore,adjoinant/bitcore,janko33bd/bitcore,initaldk/bitcore,UdjinM6/bitcore-dash,maraoz/coinforge,olalonde/bitcore,TOMOAKI12345/bitcore,bitpay/bitcore,martindale/bitcore,bitjson/bitcore,litecoin-project/litecore,MonetaryUnit/bitcore,iobond/bitcore,maraoz/coinforge,TOMOAKI12345/bitcore,litecoin-project/litecore,daxxog/clamcore,GroestlCoin/groestlcore,bilthon/bitcore,braydonf/bitcore,lekkas/bitcore,bitjson/bitcore,martindale/bitcore,williamcotton/bitcore,bitpay/bitcore,bitpay/bitcore,TeamPiggyCoin/PiggyCore,martindale/bitcore,jcvernaleo/bitcore,iobond/bitcore,adjoinant/bitcore,eordano/bitcore,MonetaryUnit/bitcore,bilthon/bitcore,bankonme/bitcore,genecyber/bitcore,iobond/bitcore,olalonde/bitcore,pnagurny/bitcore