Fixes gulp coverage
Merge pull request #582 from eordano/fix/gulpcover

WIP Fixes gulp coverage
fix jsdoc
fixes gulpfile cover and browser-test
Merge pull request #583 from eordano/fix/jsdoc

fix jsdoc
Merge pull request #584 from eordano/fix/gulpcover2

fixes gulpfile cover and browser-test
Add HDPrivateKey class
Add tests