Psd-tools

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- Improved merging of transparent layers (thanks Vladimir Timofeev);
- fixed layer merging and bounding box calculations for empty layers
(thanks Vladimir Timofeev);
- C extension is rebuilt with Cython 0.20.1.

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- `psd-tools.py` command-line interface is changed, 'debug' command is added;
- pretty-printing of internal structures;
- pymaging support is fixed;
- allow 'MeSa' to be a signature for image resource blocks
(thanks Alexey Buzanov);
- `psd_tools.debug.debug_view` utility function is fixed;
- Photoshop CC constants are added;
- Photoshop CC vector origination data is decoded;
- binary data is preserved if descriptor parsing fails;
- more verbose logging for PSD reader;
- channel data reader became more robust - now it doesn't read past
declared channel length;
- `psd-tools.py --version` command is fixed;
- `lsdk` tagged blocks parsing: this fixes some issues with layer grouping
(thanks Ivan Maradzhyiski for the bug report and the patch);
- CMYK images support is added (thanks Alexey Buzanov, Guillermo Rauch and
https://github.com/a-e-m for the help);
- Grayscale images support is added (thanks https://github.com/a-e-m);
- LittleCMS is now optional (but it is still required to get proper colors).

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- Point and Millimeter types are added to UnitFloatType (thanks Doug Ellwanger).

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- Some issues with descriptor parsing are fixed (thanks Luke Petre).

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- Python 2.x: reading data from file-like objects is fixed
(thanks Pavel Zinovkin).

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- Fixed parsing of layer groups without explicit OPEN_FOLDER mark;
- Cython extension is rebuilt with Cython 0.18.