All calls to html_requires//1 
for the page are collected and duplicates are removed. Next, the 
following steps are taken:
- Add all dependencies to the set
- Replace multiple members by‘aggregate’scripts or css 
files. see use_agregates/4.
- Order all resources by demanding that their dependencies precede the 
resource itself. Note that the ordering of resources in the dependency 
list is ignored. This implies that if the order matters the 
dependency list must be split and only the primary dependency must be 
added.