Modify the test for issue 41.

The two sets of latitudes should NOT be mappable, so make sure we crash right
when we try to do the broadcast.  If we didn't crash, then we're left with an
inconsistent object that will crash deep in the view stack when we try to
retrieve the values!

--HG--
branch : release-1.0
In interp.c, make sure we have enough values to do the interpolation.

If we don't, then fill the output array with all NaNs.

Fixes issue 46.

--HG--
branch : release-1.0
Add a test case for issue 46, now that it's (hopefully) fixed.

Couldn't add this earlier, because it would cause Python to crash hard.

--HG--
branch : release-1.0
In tools.loopover, catch any StopIteration signals emanating from the data retrieval.

Don't allow these to be thrown further up the chain, or it gets interpreted as
loopover finishing successfully from its own iterations.

Fixes issue 59.

--HG--
branch : release-1.0