[#issue-27] add attributes to configure tenancy for plutus
[#issue-27] add tenant column to plutus accounts table
[#issue-27] add factory girl helpers to reload definitions
[#issue-27] add concerns for tenancy and non-tenancy, and make sure account includes it
[#issue-27] set tenancy to false by default, and add some docs for tenancy support
[#issue-27] tenant_id should be of type integer, and not string

(got used to rails add_reference, can't help it)
Merge pull request #29 from code-mancers/issue-27-multitenancy-support

Issue 27 multitenancy support