Update dependencies + switch from govendor to dep

DEPENDENCIES.md

@@ -0,0 +1,3 @@
+# Dependency management
+
+QuotaService uses [Dep](https://golang.github.io/dep/) to manage dependencies, which in turn creates and maintains `Gopkg.lock` and all the files you see in `vendor/`.

Gopkg.toml

@@ -0,0 +1,38 @@
+# Gopkg.toml example
+#
+# Refer to https://golang.github.io/dep/docs/Gopkg.toml.html
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#   name = "github.com/x/y"
+#   version = "2.4.0"
+#
+# [prune]
+#   non-go = false
+#   go-tests = true
+#   unused-packages = true
+
+
+[[constraint]]
+  name = "gopkg.in/alecthomas/kingpin.v2"
+  version = "2.2.3"
+
+[[constraint]]
+  name = "gopkg.in/redis.v5"
+  version = "5.2.7"
+
+[prune]
+  go-tests = true
+  unused-packages = true