Add build description for travis continuous integration service.
Add build description for travis continuous integration service.

Signed-off-by: Ralph Giles <65585f72bf62a11d2f4105aa30c20fe94efea46f@thaumas.net>

eidy/vorbis,eidy/vorbis,ShiftMediaProject/vorbis,felipebetancur/vorbis,emscripten-ports/Vorbis,ksophocleous/vorbis,erikd/vorbis,ShiftMediaProject/vorbis,eidy/vorbis,youfearm3/vorbis,felipebetancur/vorbis,erikd/vorbis,emscripten-ports/Vorbis,erikd/vorbis,youfearm3/vorbis,emscripten-ports/Vorbis,nicolaichuk/vorbis,mwgoldsmith/vorbis,emscripten-ports/Vorbis,erikd/vorbis,ShiftMediaProject/vorbis,ksophocleous/vorbis,eidy/vorbis,ksophocleous/vorbis,nicolaichuk/vorbis,nicolaichuk/vorbis,youfearm3/vorbis,ShiftMediaProject/vorbis,ShiftMediaProject/vorbis,mwgoldsmith/vorbis,mwgoldsmith/vorbis,nicolaichuk/vorbis,youfearm3/vorbis,ShiftMediaProject/vorbis,mwgoldsmith/vorbis,felipebetancur/vorbis,ksophocleous/vorbis,felipebetancur/vorbis