packer: fix data race in communicator
packer/rpc: get rid of data races in tests
packer/plugin: fix data race reading stdout in Client
packer/plugin: get rid of data race setting exited for Client
packer/plugin: remove race in Exited()
communicator/ssh: get data race tests passing
Make travis run data race tests
scripts: set PACKER_RACE to build with race detector
scripts: build go get ./... early to speed up builds
v0.3.4
up version for dev
Update CHANGELOG
Merge remote-tracking branch 'upstream/master' into add-vagrant-support-for-digitalocean