v1.0.4

SymbolicUtils v1.0.4

Diff since v1.0.3

Closed issues:

• Citation (#487)

Merged pull requests:

• Add unittest for LiteralReal simplification (#501) (@MilesCranmer)
• Add upgrade guide (#508) (@YingboMa)
• activate Documenter (#510) (@ArnoStrouwen)
• Fix -x printing (#517) (@YingboMa)