Update MathematicalFunctionsTest.scala
Merge branch '2.0' of https://github.com/neo4j/cypher-refcard into 2.0

Conflicts:
	neo4j-cypher-refcard-tests/src/test/scala/org/neo4j/cypher/docgen/refcard/MathematicalFunctionsTest.scala
Merge pull request #4 from wfreeman/2.0

Better info on atan2, fixes typo.