Verify that wrapped is not None

If wrapped is None we raise a ValueError to let the user know that we
are unable to continue.
Update CHANGES for wsgiapp and wsgiapp2
Remove repeated word.

Remove repeated `use` word.
Improving `X-Vhm-Root` paragraphs.

Improving text of `X-Vhm-Root` paragraphs in `Other Backwards Incompatibilities` section.
Merge pull request #1320 from bertjwregeer/feature.raise_valueerror_wsgi

Feature: raise ValueError if wrapped is None in wsgiapp/wsgiapp2
remove redundant tests
Typo found in second Declarative code block

There were two import statements for Configurator.
I removed the second import statement in the "__main__" since most of the
documentation declares all imports on the top of the source.

	modified:   configuration.rst
Merge pull request #1323 from bmess/narrative_typo

Typo found in second Declarative code block
Merge pull request #1321 from omidraha/patch-1

Improving `X-Vhm-Root` paragraphs.