Fixes zopefoundation/persistent#18 : Make the .raw() and repr() of the Python TimeStamp match the C version in more cases. Also, make the behaviour of comparisons and hashing match as well; test all this.

fix test___setstate___interns_dict_keys failure on pypy3

(not using unittest.skipIf because it doesn't exist in python 2.6)

Also enable travis tests for 3.4 and pypy3

Intern keys in `__setstate__`

Refs zopefoundation/persistent#15

See: http://blog.travis-ci.com/2014-12-17-faster-builds-with-container-based-infrastructure/

Also, work around edge case on Travis where files aren't found.

Exclude interfaces, whose method docstrings confuse the coverage checker.

Downloaded from https://bootstrap.pypa.io/bootstrap-buildout.py.

[ci skip]

The pure-Python Persistent class no longer calls subclass's __setattr__ at instance creation time, just like the C version.

KeyError would be raised during ZODB serialization; catch that. Not sure if this is the best solution or not but it gets zope.container passing.