Xphyle

* Added basic performance testing.
* Fixed 12: xphyle not recognizing when system-level lzma not installed.

* Forcing use of backports.typing for python < 3.6.

* Added a paper for submission to JOSS.
* Enabled DOI generation using Zenodo.

* Lots of fixes for bugs and type errors using mypy.
* Two breakting changes that necessitate the major version bump:
* Several methods were erroneously named "uncompress_..." and have been corrected to "decompress_..."
* Default values were erroneously used for the char_mode and linesep parameters of fileinput(), fileoutput(), FileInput, FileOutput, and all their subclasses. textinput(), textoutput(), byteinput(), and byteoutput() convenience methods were added, and default values were set to None.

* Add get_compression_format_name() method to Formats.
* Validate the compression type in xopen.

* Switch to pytest for testing.
* Bugfixes in fileoutput.
* Add ability to specifiy a file header for each file opened by fileoutput.
* Add ability to pass initializing text/bytes to xopen with file_type==BUFFER to create a readable buffer.