4.0.0

Symbolics.jl now supports the latest symbolic computing architecture backed by Metatheory.jl v1.2 and SymbolicUtils.jl v0.18 for generic term rewriting.
Support for automatic code optimization through Metatheory.jl EGraphs and SymbolicUtils's optimize function.

3.3.0

adds simplify_fractions which turns an expression into a single fraction and simplifies by dividing the numerator and denominator factors by appropriate GCDs
Use new fraction_iszero and fraction_isone functions from SymbolicUtils to implement iszero and isone respectively.
x / x etc. are no more simplified on construction, call simplify_fractions to simplify them.