ruby version : currency, transaction, book
All tests are okay!
BookReader
BookWriter, set_balance
Multi currencies : first attempt

This does not work because transactions between books whose rates are
different, are not considered.
Merge branch 'multi-currency' into ruby
Remove Currency and related stuff
SMBC and SMBC VISA card
Merge branch 'SMBC,SMBCCard' into ruby
Parse howm files
SMBC, SMBC VISA Card

Parsing csv files works!
Delete OCaml version
Revert "Delete OCaml version"

This reverts commit b4bb7caecabb420413c63dfa66a54b98ed28bbf0.
Merge branch 'parse-options' into ruby
Delete OCaml version
Merge branch 'ruby'