v0.4

This is a big update. Added some new features.

• added processing special chars (like +, / etc) for $table parameter
• added DISTINCT for select() method
• added parameter withValues=true for getSql() method
• added methods:
  • __toString()
  • union() and unionSelect() for UNION and UNION ALL in SELECT queries
  • expects() and exceptSelect() for EXCEPT in SELECT queries
  • intersect() and intersectSelect() for INTERSECT in SELECT queries
  • getDriver()
• written unit tests for all SQL methods
• README was separated for some files
• added createView() method (CREATE VIEW view_name AS SQL_SELECT)
• added dropView() method (DROP VIEW view_name)