Bump "safe" dependencies (#200)

* cloud.google.com/go: v0.30.0 -> v0.34.0

Signed-off-by: Vincent Demeester <[email protected]>

* contrib.go.opencensus.io/exporter/stackdriver: v0.6.0 -> v0.8.0

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/aws/aws-sdk-go: v1.15.52 -> v1.16.11

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/gobuffalo/envy: v1.6.5 -> v1.6.11

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/googleapis/gax-go: v2.0.0 -> v2.0.3

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/markbates/inflect: v1.0.3 -> v1.0.4

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/prometheus/client_golang: v0.8.0 -> v0.9.2

Signed-off-by: Vincent Demeester <[email protected]>

* github.com/spf13/pflag: v1.0.2 -> v1.0.3

Signed-off-by: Vincent Demeester <[email protected]>

* go.opencensus.io: v0.14.0 -> v0.18.0

Signed-off-by: Vincent Demeester <[email protected]>

* google.golang.org/appengine: v1.2.0 -> v1.4.0

Signed-off-by: Vincent Demeester <[email protected]>

* google.golang.org/grpc: v1.15.0 -> v1.17.0

Signed-off-by: Vincent Demeester <[email protected]>

* gopkg.in/inf.v0: v0.9.0 -> v0.9.1

Signed-off-by: Vincent Demeester <[email protected]>

* gopkg.in/yaml.v2: v2.2.1 -> v2.2.2

Signed-off-by: Vincent Demeester <[email protected]>