Update spec link for Object.assign
Note that Object.getOwnPropertyDescriptors is ES7 and add spec link
Remove Object.getPropertyDescriptor and Object.getPropertyNames

These didn't make it into the spec after all.
Change "Structs" to "Typed Objects", indicate ES7 specification target and fix link to preliminary spec
Add spec link for Object.is
Merge pull request #135 from tschneidereit/gh-pages

Cleanup