build: don't fetch dependencies in TravisCI; they should be vendored
build: don't fetch dependencies in TravisCI; they should be vendored

We don't actually want to do a 'go get' for the upspin repo because all
its dependencies should be vendored. By disabling the TravisCI install
step we make sure TravisCI will fail if we introduce a dependency by
mistake.

Change-Id: I968537f36440050c0e61fa75ef2ee74febc99b57
Reviewed-on: https://upspin-review.googlesource.com/14742
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/augie,upspin/augie,upspin/augie