Previously, the GO15VENDOREXPERIMENT environment variable was unset,
leaving travis to only use the vendored packages during builds for Go
1.6 which enabled the experiment by default. Export the variable so
it also correctly tests under Go 1.5.
The vet tool moved to the Go tree as of go1.5 so it does not
need to be installed seperately. With the x/tools repo now gone,
remove the install step for vet since it fails.
This commit corrects various things found by the static checkers
(comments, unkeyed fields, return after some if/else).
Add generated files and legacy files to the whitelist to be ignored.
Catch .travis.yml up with btcd so goclean can be run.
Our policy is to only ensure the code compiles for the latest Go release
minus one version. Since Go 1.4 has now been released, this commit
updates TravisCI to remove Go 1.2 from the build matrix. While here, add
release to the matrix which should have been there before anyways.
