Fixes #18 by switching to the PyPI version of python-magic
Fixes #21 by also looking for multiline default extent expressions
This now also removes Icon|Diagram with no "graphics" annotation present
#20 Rewrite the default extent detection.

Now also `Diagram(graphics)` should get removed again.
Also made the naming a bit more consistent.
Fix typo
Merge pull request #22 from tbeu/Fix-typo

Fix typo. Thanks.
Prepare v0.5.1 release.
Adds some test files.
And back to development mode.
Merge branch 'libmagic'