Okonomiyaki

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Improvements:

* SemanticVersion class added
* MetadataVersion class added to easily manipulate metadata versions.
* PEP440Version class added.
* RuntimeVersion class added to model edm runtime versions
* IRuntimeMetadata.factory_from_path class function to parse and validate
runtime packages.
* __str__ is now implemented for EPDPlatform. The implementation support
EPDPlatform.from_epd_string(str(epd_platform)) == epd_platform (117)

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Improvements:

* EnpkgVersion.from_string now handles versions of the form `1.3.0`, with the
build number being implicitly 0.
* EggMetadata.from_egg now handles eggs built for RedHat Enterprise
Linux 3 (88).
* Fix decoding errors when parsing PKG-INFO (86)
* Fix parsing of spec/depend for RedHat 3 eggs (88)
* Special case invalid requirement 'numpy-1.8.0'

Internals:

* Remove dependency on six
* Add support for both '-' and '_' as separators between os and arch in
platform names for EPDPlatform, i.e. both from_epd_string("rh5-x86_64") and
from_epd_string("rh5_x86_64") work (83).
* Black list mechanism to fix invalid PKG-INFO
* Black list mechanism to handle platform-specific, any-arch eggs
* Add special 'private' API for brood to bypass checksum computation in
EggMetadata and PackageInfo

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Improvements:

* SetuptoolsEggMetadata now can guess ABI for legacy cases. (74)
* use PythonImplementation instances instead of strings to store python tag
(75).
* add okonomiyaki.__version_info__ for easy version comparison (76).

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New features:

* New EggRewriter class to create Enthought eggs from setuptools eggs.

Improvements:

* add EPDPlatform.from_running_python ctor (62)
* reject unsupported metadata version in PackageInfo (63)
* add support for 'py2' python tag (64)
* add support for python 3 in SetuptoolsEggMetadata (70)

Bug fixes:

* handle Enthought eggs without PKG-INFO in EggMetadata (65)
* fix unicode handling of PKG-INFO and EGG-INFO/spec/summary (72)