indexParamCallback is documented, but not properly implemented #241
Description
In httpClient.js you fail to copy indexParamCallback from options to params within the
if (this.options.indexParam) {
block (line 89) and in options.js you do not copy it from the options passed to the constructor.
It would also be very helpful to fix the documentation of the indexParam option. It's not a word to be searched for, it's a string that will be passed to new Regexp(here, 'g') and to make matters worse, the replacement will be done AFTER the URL had been split into pieces and "fixed".
In all likelihood I will not want that placeholder to be a word, but rather something containing a bunch of special characters to distinguish it from ordinary parts of the URLs and make sure it doesn't get found at unexpected places. The problem is that in all likelyhood the URL already gets f-ed up by the time you attempt to make that replacement.
These two together mean that all the usual options like {value}, [value] or %value% do not work.