Remove autotools generated files, eliminate hardcoded DEFBASE, add .travis.yml

- Other autotools-based projects I see in Github don't check in
  all the code-generated junk. They usually include an autogen.sh
  script for running autoconf to generate that stuff. So, removed
  all those ugly files. Instead, interested parties should DIY
  by invoking autogen.sh

- Got rid of DEFBASE by using @abs_top_builddir@ macro in autoconf.

- Added a .travis.yml file for Travis-CI builds... can't try it
  at the moment since Travis is under a DDoS attack, but it'd be
  nice to be able to ensure you don't break the Linux build when
  you commit from Mac.

- Add "foreign" option to AM_INIT_AUTOMAKE so it doesn't insist
  on README, COPYING, ChangeLog, NEWS. Deleted these mostly empty
  files.

- Hide more autotools generated files in .gitignore