buildGoPackage: remove Go deps file libs.json

After #16017 there were a lot
of comments saying that `nix` would be better than `JSON`
for Go packages dependency sets.
As said in https://github.com/NixOS/nixpkgs/pull/16017#issuecomment-229624046

    > Because of the content-addressable store, if two programs have the
    > same dependency it will already result in the same derivation in
    > the
    > store. Git also has compression in the pack files so it won't make
    > much difference to duplicate the dependencies on disk. And finally
    > most users will just use the binary builds so it won't make any
    > differences to them.

This PR removes `libs.json` file and puts all package dependencies in
theirs `deps.json`.

pkgs/development/tools/deis/deps.json

@@ -1,10 +1,29 @@
 [
     {
-        "include": "../../../go-modules/libs.json",
-        "packages": [
-            "github.com/docopt/docopt-go",
-            "golang.org/x/crypto",
-            "gopkg.in/yaml.v2"
-        ]
+        "goPackagePath": "gopkg.in/yaml.v2",
+        "fetch": {
+            "type": "git",
+            "url": "https://gopkg.in/yaml.v2",
+            "rev": "a83829b6f1293c91addabc89d0571c246397bbf4",
+            "sha256": "1m4dsmk90sbi17571h6pld44zxz7jc4lrnl4f27dpd1l8g5xvjhh"
+        }
+    },
+    {
+        "goPackagePath": "github.com/docopt/docopt-go",
+        "fetch": {
+            "type": "git",
+            "url": "https://github.com/docopt/docopt-go",
+            "rev": "784ddc588536785e7299f7272f39101f7faccc3f",
+            "sha256": "0wwz48jl9fvl1iknvn9dqr4gfy1qs03gxaikrxxp9gry6773v3sj"
+        }
+    },
+    {
+        "goPackagePath": "golang.org/x/crypto",
+        "fetch": {
+            "type": "git",
+            "url": "https://go.googlesource.com/crypto",
+            "rev": "575fdbe86e5dd89229707ebec0575ce7d088a4a6",
+            "sha256": "1kgv1mkw9y404pk3lcwbs0vgl133mwyp294i18jg9hp10s5d56xa"
+        }
     }
 ]