0.9.4

Full Changelog: 0.9.3...0.9.4

Update "join" related code
Use literal strings instead of Sql::* constants
Rename vars and classes according to ansi sql

0.9.3

Full Changelog: 0.9.2...0.9.3

• Simplify Element interface
• Add support for multiple combine (union, intersect, except) clauses
• Add type-declarations