fix: Use Float as Number instead of Float80

Closes #76

Tests/StencilTests/VariableSpec.swift

@@ -47,13 +47,13 @@ func testVariable() {
 
     $0.it("can resolve an integer literal") {
       let variable = Variable("5")
-      let result = try variable.resolve(context) as? Float80
+      let result = try variable.resolve(context) as? Number
       try expect(result) == 5
     }
 
     $0.it("can resolve an float literal") {
       let variable = Variable("3.14")
-      let result = try variable.resolve(context) as? Float80
+      let result = try variable.resolve(context) as? Number
       try expect(result) == 3.14
     }