TST: Moving testing method outside of TestCase
Make assert_numpy_array_equal available without subclassing TestCase; see #8023

If this is not along the lines of what you have in mind for #8023, please feel free to close this.
 this is fine

the idea is that all module level functions should be available on TestCase (and vice versa)

you can prob do this automatically 

by creating methods for all assert_\* in the module on TestCase
 @jreback is this OK to merge?

I think the automatic adding of methods to TestCase can be done later in another PR, this is just adding the two test functions to the main testing namespace

@bwignall Can you squash the two commits?
 yep this is ok
 @bwignall sorry, I forgot this PR, and it is now already merged as part of another one, see  #8923 
But thanks for your work!
