fix: coverage by fixing busted's lua path

By default busted lua path is './src', which broke since
b60eec9. This gives busted the
'./?.lua' path, which works for require "kong.*".

.busted

@@ -0,0 +1,5 @@
+return {
+  default = {
+    lpath = "./?.lua;"
+  }
+}

spec/unit/stub_coverage_spec.lua

@@ -6,7 +6,7 @@ local IO = require "kong.tools.io"
 -- Stub DAO for lapis controllers
 _G.dao = {}
 
-local lua_sources = IO.retrieve_files(".//kong", { exclude_dir_pattern = "cli", file_pattern = ".lua" })
+local lua_sources = IO.retrieve_files("./kong", { exclude_dir_pattern = "cli", file_pattern = ".lua" })
 
 for _, source_link in ipairs(lua_sources) do
   local source_file = dofile(source_link)

spec/unit/utils_spec.lua

@@ -5,7 +5,7 @@ describe("Utils #tools", function()
 
   describe("Stringy", function()
 
-    it("should work when using startsiwth", function() 
+    it("should work when using startsiwth", function()
       local stringy = require "stringy"
       assert.truthy(stringy.startswith("hello", "he"))
       assert.falsy(stringy.startswith("hello", "HE"))