Merge branch 'mcuelenaere-nano-support'

Vertcoin segwit addresses support

Dropped Node 4 support

chore(release): 0.2.1

refactored segwit support

chore(release): 0.1.7

chore(release): 0.1.6

chore(release): 0.1.5

chore(release): 0.1.4

chore(release): 0.1.3