readme: Remove "www." from pledgie.com https url 

The SSL certificate served on https://www.pledgie.com is invalid
as it is for pledgie.com, not www.pledgie.com.

The url was blocked in modern browsers (such as Chrome).

Kept anchor url on HTTP as their HTTPS site is a mess (all urls
still point to HTTP, individual resources such as images work fine
over HTTPS, which is to make sure the image url isn't blocked when
using GitHub, which is HTTPS enforced).
Merge pull request #171 from Krinkle/develop

readme: Remove "www." from pledgie.com https url