SQLPrimaryKeys: Implementation and tests.
SQLPrimaryKeys: Removed an accidental escape on a double quote
SQLPrimaryKeys: modified query to join on table_constraints
SQLPrimaryKey: created a multiple_column_pk table in the tests
SQLPrimaryKeys: return error if no schema provided
SQLPrimaryKeys: updated a comment in the test
SQLPrimaryKeys: modify query to join on constraint_schema
Merge pull request #16 from louisrli/sqlprimarykeys

SQLPrimaryKeys