Fix parsing invalid input

i.e. `x = 1.xe` — because parseFloat("1.xe") returns 1, this parsed as
`x = 1`.

Ref #857

lib/parse.js

@@ -182,7 +182,8 @@ function parse_js_number(num) {
     } else if (RE_OCT_NUMBER.test(num)) {
         return parseInt(num.substr(1), 8);
     } else {
-        return parseFloat(num);
+        var val = parseFloat(num);
+        if (val == num) return val;
     }
 };