Bugfix/lesson 6

[emxqm-11]

In main.go:

• fix migrations.Migrate() and removed migrations.MigrateTransaction() which is nonexistent
• CreateTransaction was missing Amount so the logs for transactions would always show 0 for amount recorded in postgresql
• i added a lot of debugging errors i got to README so it can be helpful to others.
• function Transaction()'s updateAccount logic for adding amount to the toAccount was wrong. It used the fromAccount by mistake. Line 56.

[emxqm-11]

@radoslawfabisiak Let me know if you want any changes, i know the README was a big change but the rest were bug fixes. Also great work on this tutorial, i loved it ! Hence I wanted to contribute.