Improve test support

• Use unittest.mock when available. This removes the mock dependency on Python 3.
• Tests no longer need to mock out pyramid_sqlalchemy.includeme; this is now handled by DatabaseTestCase and the py.test fixtures.
• Automatically make py.test fixtures available externally. This removes the need to copy & paste them over from the documentation.
• Fix error on pytest fixture example.
• Setup Travis to
  automatically run tests on CPython 2.6, CPython 2.7, CPython 3.3, CPython 3.4
  and PyPy.

Small feature release

• Add missing schema to the Pyramid-URL in the package description. This broke
  ReST rendering on the PyPI page.
• Add a new enable_sql_two_phase_commit() configuration directive to enable
  two-phase commit.
• Enable foreign key constraint checking for SQLite in DatabaseTestCase.
• Use SQLAlchemy events instead of ZopeTransactionExtension to handle
  integration of zope.sqlalchemy and SQLAlchemy.

Initial release

1.0

Prepare for 1.0 release.