Merge pull request #43 from ttyS15/master

Defend cache from model changes
Cleaned up "model change defense" pull request
Optimized and corrected stamp_fields()

Long strings could be time consuming to repeatedly hash.

And no point in sorting fields, except for messing with django-pickling:
reordering fields with no other changes will brake its pickles.
Upped version to 1.0.0 and dev status to stable
Docs for file cache
Test for #44
Marked test_44 as expected failure
Added .delete() method to simple cache
.invalidate() method for @cached() functions
Docs for .delete() and .invalidate() in simple and file cache
Removed a couple of bizare TODO items
Minor README fixes
Shortened long lines
Upped to 1.0.1
Better cache_on_save cache write

- don't use @cached_as(), which means no lambda signature to extra
  and no unnecessary redis GET request
- use .order_by() to mimic QuerySet.get() behaviour

Should help with #45
test for issue 45
Merge pull request #46 from bourivouh/master

Test for #45
Added "Writing a test" entry to README
Updated CHANGELOG
Updated LICENSE (c) years