fix: Prometheus dependencies

Prometheus is related to `go-kit/kit`.
`go-kit/kit` doesn't have dependency manager.

We use `go-kit/kit` v0.3.0 (15 Nov 2016).

We must explicitly declare the Prometheus dependencies.
Prometheus doesn't have dependency manager.
Use the commit date to fixed all hash.

refs:
- go-kit
  - https://github.com/go-kit/kit/tree/v0.3.0 (15 Nov 2016)
- Prometheus
  - https://github.com/prometheus/client_golang/commits/master
  - 08fd2e1237 (Apr 1, 2017)
  - https://github.com/prometheus/common/commits/master
  - 49fee292b2 (Feb 20, 2017)
  - https://github.com/prometheus/client_model/commits/master
  - 6f38060186 (Feb 16, 2017, master, HEAD)
  - https://github.com/prometheus/procfs/commits/master
  - a1dba9ce8b (Feb 16, 2017)

glide.yaml

@@ -108,6 +108,16 @@ import:
   version: v0.3.0
   subpackages:
   - metrics
+- package: github.com/prometheus/client_golang
+  version: 08fd2e12372a66e68e30523c7642e0cbc3e4fbde
+  subpackages:
+  - prometheus
+- package: github.com/prometheus/common
+  version: 49fee292b27bfff7f354ee0f64e1bc4850462edf
+- package: github.com/prometheus/client_model
+  version: 6f3806018612930941127f2a7c6c453ba2c527d2
+- package: github.com/prometheus/procfs
+  version: a1dba9ce8baed984a2495b658c82687f8157b98f
 - package: github.com/eapache/channels
   version: v1.1.0
 - package: golang.org/x/sys