Psd-tools3

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- implemented extraction of embedded files (embedded smart objects) -
thanks Volker Braun;
- optional C extension is rebuilt with Cython 0.21.2.
- hg mirror on bitbucket is dropped, sorry!

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- improved METADATA_SETTING decoding (thanks Evgeny Kopylov);
- layer comps decoding (thanks Evgeny Kopylov);
- improved smart objects decoding (thanks Joey Gentry);
- user API for getting layer transforms and placed layer size
(thanks Joey Gentry);
- IPython import is deferred to speedup ``psd-tools.py`` command-line utility;
- ``_RootGroup.__repr__`` is fixed;
- warning message building is more robust;
- optional C extension is rebuilt with Cython 0.21.1.

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- Fixed reading of images with layer masks (thanks Evgeny Kopylov);
- improved mask data decoding (thanks Evgeny Kopylov);
- fixed syncronization in case of ``8B64`` signatures (thanks Evgeny Kopylov);
- fixed reading of layers with zero length (thanks Evgeny Kopylov);
- fixed Descriptor parsing (thanks Evgeny Kopylov);
- some of the descriptor structures and tagged block constants are renamed (thanks Evgeny Kopylov);
- PATH_SELECTION_STATE decoding (thanks Evgeny Kopylov);
- the library is switched to setuptools; docopt is now installed automatically.

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- Layer effects parsing (thanks Evgeny Kopylov);
- trailing null bytes are stripped from descriptor strings
(thanks Evgeny Kopylov);
- "Reference" and "List" descriptor parsing is fixed
(thanks Evgeny Kopylov);
- scalar descriptor values (doubles, floats, booleans) are now returned
as scalars, not as lists of size 1 (thanks Evgeny Kopylov);
- fixed reading of EngineData past declared length
(thanks Carlton P. Taylor);
- "background color" Image Resource parsing (thanks Evgeny Kopylov);
- `psd_tools.decoder.actions.Enum.enum` field is renamed to
`psd_tools.decoder.actions.Enum.value` (thanks Evgeny Kopylov);
- code simplification - constants are now bytestrings as they should be
(thanks Evgeny Kopylov);
- Python 3.4 is supported.

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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).