Merge pull request #647 from sys27/sys27-patch-1

Update README.md

Author: sys27

README.md

@@ -40,9 +40,9 @@ var exp = processor.Parse("2 + x");
 
 // 'exp' has a parameter
 // we should provide a value for variable 'x'
-var parameters = new ParameterCollection
+var parameters = new ExpressionParameters
 {
-    { "x", 10 }
+    new Parameter("x", 10)
 };
 var result = exp.Execute(parameters);
 
@@ -118,10 +118,10 @@ processor.Differentiate("2x + sin(y)", new Variable("x")); // will return "2"
 | ------: | ------ | ------------: | --------: |
 |   3.7.3 | Parse  |   39,567.9 ns |   63736 B |
 |   4.0.0 | Parse  |  9,128.180 ns |    4760 B |
-|   4.2.0 | Parse  |  14,574.60 ns |    4760 B |
+|   4.2.0 | Parse  |  14,855.62 ns |    4872 B |
 |   3.7.3 | Solve  |   55,260.0 ns |   96920 B |
 |   4.0.0 | Solve  | 15,319.497 ns |   10672 B |
-|   4.2.0 | Solve  |  24,909.03 ns |   10672 B |
+|   4.2.0 | Solve  |  22,074.89 ns |   9936 B |
 
 [More details](https://github.com/sys27/xFunc/wiki/Performance-Comparison)