travis: Add a minimal build configuration.

This is a continuous integration service integrated with github.

This just invokes 'make check'. 'make distcheck' fails with a permission issue:

    cannot move `/home/travis/build/rillian/vorbis-tools/vorbis-tools-1.4.0/_build/po/sv.new.po' to `sv.po': Permission denied

.travis.yml

@@ -0,0 +1,12 @@
+language: c
+
+addons:
+  apt:
+    packages:
+      - libogg-dev
+      - libvorbis-dev
+
+script:
+  - ./autogen.sh
+  - ./configure
+  - make -j2 V=1 check