vendor: add missing deps and remove go get in .travis.yml

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

vendor.conf

@@ -37,11 +37,18 @@ github.com/opencontainers/runc v1.0.0-rc2
 # OCI runtime spec, latest release as of 12/16/2016
 github.com/opencontainers/runtime-spec v1.0.0-rc3
 # logrus, latest release as of 12/16/2016
+# FIXME: github.com/docker/docker/pkg/archive requires this pkg as github.com/Sirupsen/logrus.
+# So we vendor github.com/Sirupsen as well.
 github.com/sirupsen/logrus v0.11.0
+github.com/Sirupsen/logrus v0.11.0
 # go-btrfs from stevvooe; master as of 1/11/2017
 github.com/stevvooe/go-btrfs 029908fedf190147f3f673b0db7c836f83a6a6be
 # testify go testing support; latest release as of 12/16/2016
 github.com/stretchr/testify v1.1.4
+# go-spew (required by testify); latest release as of 1/12/2017
+github.com/davecgh/go-spew v1.1.0
+# go-difflib (required by testify); latest release as of 1/12/2017
+github.com/pmezard/go-difflib v1.0.0
 # Go pkg for handling fifos; master as of 12/16/2016
 github.com/tonistiigi/fifo fe870ccf293940774c2b44e23f6c71fff8f7547d
 # client application library; latest release as of 12/16/2016
@@ -54,3 +61,9 @@ golang.org/x/crypto 01be46f62051d02cb6a36c9b47b37b24e5758c81
 google.golang.org/grpc v1.0.5
 # pkg/errors; latest release as of 12/16/2016
 github.com/pkg/errors v0.8.0
+# lockfile; master as of 1/12/2017
+github.com/nightlyone/lockfile 1d49c987357a327b5b03aa84cbddd582c328615d
+# docker (for docker/pkg/archive, which is required by snapshot); latest experimental release as of 1/12/2017
+github.com/docker/docker v1.13.0-rc6
+# go-digest; master as of 1/12/2017
+github.com/opencontainers/go-digest 21dfd564fd89c944783d00d069f33e3e7123c448