Update copyright years on Sphinx docs.
Fix encrypting to filenames and/or file-like objects.

 * FIXES Issue#24, which prevented python-gnupg from encrypting to a
   filename given as a string to the `output` parameter of
   `gnupg.GPGMeta._encrypt()`.

 * THANKS TO by Bill Buddington of SecureDrop and Yan Zhu of the
   Electronic Frontier Foundation (EFF) for finding and reporting the
   bug. The ticket for this bug can be viewed at:
   https://github.com/isislovecruft/python-gnupg/issues/24
Add new unittest that tests encryption with a filename output.

 * ADD test_encryption_to_filename which checks that encrypt(...,
   output='somefilename.gpg') works correctly (when `output` is a string
   containing the filename).
   This tests for the bug reported in Issue #24.
   https://github.com/isislovecruft/python-gnupg/issues/24
Add unittest which tests encrypt() when `output` is given an open file.

 * ADD new unittest, `test_encryption_to_filehandle`.
Remove `sudo` from `uninstall` directive in Makefile.
Merge branch 'fix/24-output-to-filename' into develop
Merge branch 'release/1.3.1'
Merge branch 'master' into develop