code: function runStringHandlers(declarations, stringHandlers) {
      var result = {};
  
      Object.keys(declarations).forEach(function (key) {
          // If a handler exists for this particular key, let it interpret
          // that value first before continuing
          if (stringHandlers && stringHandlers.hasOwnProperty(key)) {
              result[key] = stringHandlers[key](declarations[key]);
          } else {
              result[key] = declarations[key];
          }
      });
  
      return result;
  }
docs: Helper method of generateCSSRuleset to facilitate custom handling of certain
  CSS properties. Used for e.g. font families.
  
  See generateCSSRuleset for usage and documentation of paramater types.