add support for comparison operators.

README.md

@@ -49,6 +49,7 @@ The following predicates are built-in to rusty-wam.
 * Arithmetic support:
     * is/2 works for `(+)/2`, `(-)/{1,2}`, `(*)/2`, `(//)/2`, `(div)/2`, `(/)/2`, `(rdiv)/2`,
       `(xor)/2`, `(rem)/2`, `(mod)/2`, `(/\)/2`, `(\/)/2`, `(>>)/2`, `(<<)/2`.
+    * Comparison operators: `>`, `<`, `=<`, `>=`, `=:=`, `=\\=`.
 * `atomic/1`
 * `call/N` (1 <= N <= 63)
 * `catch/3`