Change the API to improve initialisation

[chrisvanmook]

Instead of passing an object, it would be nice to have something like this instead:

instance
    .urlBase('https://LINK.TO.DOMAIN')
    .siteId(3)
    .setUserId('example_id')
    .disableCookies()
    .setSecureCookie(true)
    .setRequestMethod('POST');

#174 (comment)

[An-dz]

That would be similar to my tinta package.

It would need some sort of run method to execute the injector (insertBefore). This could be the first thing called on trackEvents for JS and on createInstance for React. Without this it can't be injected on the page as every method injects on window._paq and it's impossible to know if the chain has ended.

[chrisvanmook]

As mentioned here we should also keep in mind that some settings should also be able to set after initialisation