Clean the database initialize process, and fix the bug that --name is…

[huyx]

When I use the following command:

fake2db --db sqlite --name test.db --rows 100

Instead of using test.db as the database file name, fake2db use a generated filename such as sqlite_JZMYNRKM.db.

I hope I had fixed the problem, but it is not full tested for other engine(postgresql, mysql, ...).

Thanks a lot.

[bhrgu]

Hi!
Your PR looks like a bugfix for #35.
I ran few tests with your code locally for SQLite and MySQL with no errors (except #39). BTW, PostgreSQL doesn't affected by this issue.

[emirozer]

Thanks for the PR, I will be releasing a new version this week. This pr will be included