Switch to using geotrellis master branch
Quiet make output for Travis...

But not too much, or Travis will fail if no output in 10 minutes, so leaving warnings.
Skip PostGIS compile for Travis (already there)
Explicitly specify master branch for geotrellis
Merge pull request #32 from flibbertigibbet/feature/change-geotrellis-branch

Switch to using geotrellis master branch