Changelog for simple-smt-0.6.0

0.6.0: Allow finer-grained logging 0.5.5: Add support for unsupported results 0.5.3: Add 'zeroExtend' and 'signExtend' 0.5.2: Fix right shift 0.5.1: Add 'define' commands 0.5: Adds more bit-wise operations 0.4: Fixes definiiton of `geq`