Document the deprecation.

Hopefully all modules whose imports legitimately result in a skipped
test have been properly wrapped by the previous commits.

deprecated flag from get_attribute since it isn't likely
to do anything useful.

directory by consensus of devs at pycon sprint.

Adds unittests to make sure the old fail* names continue to work now
and adds a comment that they are pending deprecation.

Also adds a test to confirm that the plural Equals method variants
continue to exist even though we're unlikely to deprecate those.

http://bugs.python.org/issue2578

return the error message produced by importlib, so that if an import
in the package whose import is being wrapped is what failed the skip
message will contain the name of that module instead of the name of the
wrapped module.  Also fixed formatting of some previous comments.

tuples, dicts and sets on failure.

Many new handy type and comparison specific assert* methods have been added
that fail with error messages actually useful for debugging.  Contributed in
by Google and completed with help from mfoord and GvR at PyCon 2009 sprints.

Discussion lives in http://bugs.python.org/issue2578.

#1386675: specify WindowsError as the exception, because it has a winerror attribute that EnvironmentError doesnt have.