Release version 0.4.0 of bigfloat

REL: Tag 0.3.0 release.

Release notes
-------------

Major changes since version 0.2.1:

- The bigfloat package uses Cython rather than ctypes.

- The bigfloat package now supports both Python 2 and Python 3.  However,
  note that Python 2.5 and earlier versions are no longer supported.

- Development moved from Bitbucket to GitHub; repository converted from
  Mercurial to Git.

- Documentation now hosted on Read the Docs.

For more details, see CHANGELOG.rst.

REL: v0.3.0a2.

REL: v0.3.0a1

REL: v0.2.1.

REL: v0.2.

REL: v0.1.2.

REL: v0.1.1.

REL: v0.1.

REL: Tagging 0.3.0b1 release.

Highlights of this release:

- complete migration to Cython; remove old ctypes-based code
- Use a single codebase to support both Python 2 and Python 3.
- Support for Python version 2.5 and older has been dropped.