Log Message:
Upgrade to PyGreSQL 3.7

Important changes from PyGreSQL 3.6.2 to PyGreSQL 3.7
  - Fixes to quoting function.
  - Use Python datetime if mxDatetime is not available.
  - Add checks for valid database connection to methods.
  - Improved namespace support, handle search_path correctly.
  - Removed old dust and unnessesary imports, added docstrings.
  - Internal sql statements as one-liners, smoothed out ugly code.
  - Major improvements in classic pg module.