Update functions/url/http_build_query.js

1. Instead of ugly 'cat1%5Bkey1%5D=value1&cat1%5Bkey2%5D=value2' 
my version will return more pretty and readable 'cat1[key1]=value1&cat1[key2]=value2'.
2. Simple arrays were generated as 'cat[0]=value1&cat[1]=value2' 
and now they looks like 'cat[]=value1&cat[]=value2' (without redundant numeric indexes)