Update dependencies before new release

[holgerd77]

Dependencies on this library are pretty outdated and should be updated and tested before a new release.

Short dependency analysis:

Name	Installed (noted, max)	Latest	Notes
aes-js	^0.2.3, 0.2.3	3.1.0	Major API changes, no known security fixes
bs58check	^1.0.8, 1.3.3	2.1.1	Minor fixes, no known security fixes
ethereumjs-util	^4.4.0, 4.5.0	5.1.3	Some breaking changes, serious bug fixes
hdkey	^0.7.0, 0.7.1	0.7.1	Still latest release (though old)
scrypt.js	^0.2.0, 0.2.0	0.2.0	Still latest release (though old)