fix(eslint): resolve no-mixed-operators error

Author: Hans Kristian Flaatten

index.js

@@ -187,7 +187,7 @@ module.exports.prototype.parseStringVal = function parseStringVal(string) {
  } else if (this.string.toBoolean && string.toLowerCase() === 'false') {
  return false;
  } else if (this.string.toNumber && !isNaN(parseInt(string, 10)) &&
- (+string - +string + 1) >= 0) {
+ ((+string - +string) + 1) >= 0) {
  return parseFloat(string, 10);
  }