fix procedure object_id retrieval

In Oracle 12c (and maybe 11g) the object_id for a package
procedure is not the same in all_procedures and all_objects.
spec_helper: allow customizing db service name

This allows running tests over fully qualified db service
name which doesn't match the database name
schema_spec: connect to service via service name

Use DATABASE_SERVICE_NAME instead of DATABASE_NAME when connecting to
database service directly (i.e. not via TNS).
Merge pull request #55 from javornikolov/enable-running-tests-on-fully-qualified-db-service-name

Allow running tests over fully qualified db service name which doesn't match the database name
Merge pull request #54 from javornikolov/fix-wrong-package-procedure-object-id-12c

fix procedure object_id retrieval (as it may be different in all_procedures vs all_objects)
Migrate specs to new rspec (3.x) syntax
Gemfile: bump up rspec to 3.1