Release 0.4.0

Release 0.4.0 is a addition of functionality.

• Added:
  • The reader now supports an arbitrary opener callable to handle various compression formats. Default behavior is unchanged. See documentation for examples.
  • An opener to handle gzip-compressed files is provided as sdds.reader.gzip_opener.

What's Changed

• fix test for 2 dimensional file by @JoschD in #56
• Gzip reading and compression abstraction by @fsoubelet in #58

Full Changelog: 0.3.1...v0.4.0