use getElementsByTagNameNS for namespaced DZI xml when getElementsByTagName fails
check length instead of undefined for DisplayRect nodes tagname ns fallback
correct typo in fallback ns logic for pulling display rect nodes
always use getElementsByTagNameNS since it will work for DZI xml with or without ns prefix
Merge pull request #465 from rlskoeser/ns-aware

Support dzi xml with namespaces in Firefox
Merge branch 'master' of github.com:openseadragon/openseadragon
Merge branch 'master' into collections