No longer overriding devise create method. Instead
renamed build_tenant to find_or_create_tenant  and moved it to
user model.

Also moved set_rights to user mode.
Rights are set in after_create at the user model

Added two new fields to user model current_subdomain and subdomain.
The same were added in the registrations view and the nested fields
were removed.

spec/spec_helper -> removed before and after methods and the test
db is no longer wiped.

Changed database_cleaner's strategy to truncation.

Wrote specs for registrations controller.