Update nlopes/slack vendor

vendor/github.com/nlopes/slack/Gopkg.lock

@@ -0,0 +1,33 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/davecgh/go-spew"
+  packages = ["spew"]
+  revision = "346938d642f2ec3594ed81d874461961cd0faa76"
+  version = "v1.1.0"
+
+[[projects]]
+  name = "github.com/gorilla/websocket"
+  packages = ["."]
+  revision = "ea4d1f681babbce9545c9c5f3d5194a789c89f5b"
+  version = "v1.2.0"
+
+[[projects]]
+  name = "github.com/pmezard/go-difflib"
+  packages = ["difflib"]
+  revision = "792786c7400a136282c1664665ae0a8db921c6c2"
+  version = "v1.0.0"
+
+[[projects]]
+  name = "github.com/stretchr/testify"
+  packages = ["assert"]
+  revision = "f35b8ab0b5a2cef36673838d662e249dd9c94686"
+  version = "v1.2.2"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "888307bf47ee004aaaa4c45e6139929b4984f2253e48e382246bfb8c66f3cd65"
+  solver-name = "gps-cdcl"
+  solver-version = 1