Only inline GitTracker's files

We don't want to try inlining something from stdlib, for example.

Author: stevenharman

lib/git_tracker/standalone.rb

@@ -41,8 +41,8 @@ def save(filename, path: ".")
     def each_source_file
       GIT_TRACKER_ROOT.join("lib/git_tracker.rb").open("r") do |main|
         main.each_line do |req|
-          if req =~ /^require\s+["'](.+)["']/
-            yield GIT_TRACKER_ROOT.join("lib/#{$1}.rb").to_path
+          if req =~ /^require\s+["']git_tracker\/(.+)["']/
+            yield GIT_TRACKER_ROOT.join("lib/git_tracker/#{$1}.rb").to_path
           end
         end
       end