Replace table with view as tracking interface in Greenplum adapter
WIP to replace tracking table with tracking view
Add support for coveralls.io test coverage metrics
Generalize tracking relation name; remove views from Sqlite, PostgreSQL
Trim the GP adapter, add drop view to PostgreSQL
Merge branch 'master' into track_with_view
Add Greenplum test environment for CI
Fix typo in Greenplum adapter
Require postgresql.rb in Greenplum adapter
Fix typo in Greenplum adapter
Fix crashes in Greenplum tracking view creation
Add rules to apply operations on the tracker view to the underlying table instead
Fix typo
Fix crash on dropping view during teardown
Fix crash on typo in Postgres.drop_view
Upcase enum'd values in tracker relations to match GP system tables
Fix edge cases in Greenplum tracking view

1. Make sure a dropped table doesn't show up in the tracking view,
even if it was dropped outside the application via SQL in psql.
2. Remove ANALYZE and VACUUM ops from the tracking view since these
don't say anything about the updated-ness of the data in the tables
and they shouldn't override operations that do (e.g. insert, update).
3. pg_stat_operations has a null value for subtype for TRUNCATE
operations, so add a manual fix for this column for the TRUNCATE op.
Fix tests to fix crash on unsupported updates on GP distribution keys
Add view_exists? to PostgreSQL/GP; add view tests
Add DROP CASCADE behavior to Sqlite.drop_table