Ch06 3 transaction#2

Merged

mxv2 merged 3 commits intomasterfrom

ch06-3-transaction

May 28, 2019

Commits on May 19, 2019

implement Transaction class
Maksim Kiryanov
committed

Commits on May 22, 2019

fix Transaction#usd calculation
Maksim Kiryanov
committed

Commits on May 28, 2019

implement Account class
Maksim Kiryanov
committed