Fix tests that depended on old github location

* Two tests depended on the following file existing:
  github/gollum/master/test/file_view/1_file.txt

lib/gollum/markup.rb

@@ -470,7 +470,7 @@ module Gollum
         # Use empty string if $2 is nil.
         uri = $2 || ''
         # Detect local file.
-        if uri[0..6] != 'github/'
+        if uri[0..6] != 'gollum/'
             if file = self.find_file(uri, @wiki.ref)
               contents = file.raw_data
             else

test/test_gitcode.rb

@@ -18,7 +18,7 @@ context "gitcode" do
     @wiki, @path, @cleanup = WikiFactory.create 'examples/test.git'
 
     # given
-    p = page_with_content "a\n\n```html:github/gollum/master/test/file_view/1_file.txt```\n\nb"
+    p = page_with_content "a\n\n```html:gollum/gollum/master/test/file_view/1_file.txt```\n\nb"
 
     # when rendering the page
     @rendered = Gollum::Markup.new(p).render
@@ -29,7 +29,7 @@ context "gitcode" do
   end
 
   test 'contents' do
-    g = Gollum::Gitcode.new 'github/gollum/master/test/file_view/1_file.txt'
+    g = Gollum::Gitcode.new 'gollum/gollum/master/test/file_view/1_file.txt'
 
     assert_equal g.contents, %{<ol class=\"tree\">\n  <li class=\"file\">\n    <a href=\"0\"><span class=\"icon\"></span>0</a>\n  </li>\n</ol>\n}
   end