Update README.md to point to v1.2
Code clean up
Assertions may only refer to input variables

Allowing assertions to refer to local and output variables caused
dependency analysis to be very complicated and expensive.
Warn on unused assertions and properties in subnodes
Support for CVC4
Increase version number
Extract SMT-LIB2 solver
Support z3
Code clean up
Clean up labels
Expand 'div' for CVC4
Improve performance of div in CVC4
No need for unsat cores in Z3
Update link to v1.3
Expand not-equal for SMT-LIB 2 compatibility
Fix use of BigDecimal in place of fractions
4 new examples
Improved examples
More efficient queries for z3
Handle missing values in yices result