fix(kontemplate): Make build compatible with readTree

The kontemplate build will keep using `buildGoPackage` for now until
I've had the time to add tests to //nix/buildGo

ops/kontemplate/README.md

@@ -1,8 +1,6 @@
 Kontemplate - A simple Kubernetes templater
 ===========================================
 
-[![Build Status](https://travis-ci.org/tazjin/kontemplate.svg?branch=master)](https://travis-ci.org/tazjin/kontemplate)
-
 [Kontemplate][] is a simple CLI tool that can take sets of Kubernetes resource
 files with placeholders and insert values per environment.
 

ops/kontemplate/default.nix

@@ -10,9 +10,9 @@
 # This file is the Nix derivation used to install Kontemplate on
 # Nix-based systems.
 
-{ pkgs ? import <nixpkgs> {} }:
+{ pkgs, ... }:
 
-with pkgs; buildGoPackage rec {
+with pkgs.third_party; buildGoPackage rec {
   name = "kontemplate-${version}";
   version = "master";
   src = ./.;