Optimize Attribute#iterator It allocates a lot of memory during the parsing through ParseSettings#normalizeAttributes. this new implementation just wrap the LinkedHashMap values iterator in a read-only iterator.
Optimize Attribute#iterator
It allocates a lot of memory during the parsing through
ParseSettings#normalizeAttributes.
this new implementation just wrap the LinkedHashMap values iterator in a
read-only iterator.

Iterating 1000 times over htmltests/yahoo-article-1.html was allocating
970Mb, with this optimization it's now 350Mb

Fixes #754
jhy/jsoup,angcyo/jsoup,offa/jsoup,offa/jsoup,angcyo/jsoup,jhy/jsoup