Remove unused .travis.yml file.

It wouldn't be very nice to test this on Travis for three versions of
Python, because some of the integration tests generate keys, and
although this is usually done with a UID comment saying `(INSECURE!)`
in order to trigger libgcrypt's use of the dummy RNG, the testing
process is still a little brutal on heavily used headless machines.
Remove generated MANIFEST file in `cleanup-build` Makefile directive.
Add a `cleanup-dist` Makefile directive.
Add an `upload` Makefile directive for uploading to PyPI.
Close process FDs after __init__() sanity check.

 * FIXES and issue discovered by ttanner (https://github.com/ttanner)
   in `gnupg._meta.GPGBase._check_sane_and_get_gpg_version()` where the
   GnuPG process wasn't closed and its file descriptors were left
   hanging.

 * FIXES part of Issue #63.
   https://github.com/isislovecruft/python-gnupg/issues/63

   There were so many hanging FD issues when I started patching
   upstream python-gnupg ― I doubt I found all of them. I probably even
   introduced some along the way. And, as ttanner pointed out, this
   patch doesn't fix the issue fully, so there are likely more.
Merge branch 'fix/63-hanging-fd' into develop
Merge branch 'release/1.3.2'
Merge branch 'master' into develop