ENH: Print full metadata with --info

https://www.pivotaltracker.com/story/show/34964983

This modification causes enpkg --info <pkgname> to print all available metadata for each available version of <pkgname>.

For review.  Sample output:

$ enpkg -i ipython
Package: ipython
ipython-0.13.1-1.egg was installed on: Wed Aug 29 01:12:50 2012
Version: 0.10.1-2
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:10:58
    Type: egg
    MD5: 033a5f3e637b257721366f062a73edad
    Size: 1715496
    Requirements: appinst
Version: 0.10.2-1
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:04:07
    Type: egg
    MD5: 5f0215589ef22a97cfc21adba9728802
    Size: 1716352
    Requirements: appinst
Version: 0.10.2-2
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:12:18
    Type: egg
    MD5: 8f789a6717fcb59a4540c042ceff617d
    Size: 1716349
    Requirements: appinst
Version: 0.11rc1-1
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:04:32
    Type: egg
    MD5: 963b3ecee2b19700763e2a669f38209c
    Size: 2194184
    Requirements: appinst
Version: 0.11rc4-1
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:13:25
    Type: egg
    MD5: 017934b423fdec13c40647cbfc556636
    Size: 1972312
    Requirements: appinst
Version: 0.11-1
    Product: free
    Available: True
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:06:18
    Type: egg
    MD5: 4ffdcc6f33675243bcd84aae461f0341
    Size: 1975346
    Requirements: appinst
Version: 0.12rc1-1
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:05:04
    Type: egg
    MD5: 0feac77bc9873dc049ede224511025ac
    Size: 2693729
    Requirements: appinst
Version: 0.12-1
    Product: free
    Available: True
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-02-21 14:09:15
    Type: egg
    MD5: cf527a147d1513e2ebd0186d1fd4737e
    Size: 2719992
    Requirements: appinst
Version: 0.12-2
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-04-09 18:20:34
    Type: egg
    MD5: b9a2208cf20c28afe7de5f0704709413
    Size: 2719992
    Requirements: appinst
Version: 0.12.1-1
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-04-26 14:36:56
    Type: egg
    MD5: 9b4708670cd639fae7fc44df419e6944
    Size: 2747638
    Requirements: appinst
Version: 0.12.1-2
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-05-24 12:19:24
    Type: egg
    MD5: bbc54bb685d7e7bacb2adaba4a13af03
    Size: 2747667
    Requirements: appinst
Version: 0.12.1-3
    Product: commercial
    Available: False
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-06-28 14:34:13
    Type: egg
    MD5: 2cf95c3c0a773033f8f3895337c14e09
    Size: 2720503
    Requirements: appinst
Version: 0.13.1-1
    Product: free
    Available: True
    Python version: 2.7
    Store location: https://api.enthought.com/eggs/osx-32/
    Last modified: 2012-07-13 14:41:40
    Type: egg
    MD5: 8643ba61cf0ecb9094ebda1319f861ad
    Size: 2669685
    Requirements: appinst
Merge pull request #59 from enthought/feature/full-metadata-info

ENH: Print full metadata with --info