Fix working with separate schemas

[attilahorvath]

Context

PostgreSQL allows working with multiple separate schemas and enum types can be present with the same name across them.

The gem is using the pg_type system catalog to access the different enum types, however this returns all enums from all existing schemas in the DB instead of just the currently selected ones, potentially leading to conflicts. This can be fixed by using the current_schemas(true) function which returns the schemas present in the current search path.

What's inside

• Change the queries using pg_type to filter for the current schemas only
• Specs
• Readme update to run the specs as rake spec doesn't seem to work for me

Checklist:

• I have added tests
• I have made corresponding changes to the documentation

[bibendi]

Thank you for the fix!