Revert "ignore *.orig files"

As per the discussion at
activemerchant@3c12b5, the
.gitignore file should only have project-specific artifacts in it;
developer specific artifacts should go in each developer's global
gitignore file.

This reverts commit 3c12b54.

.gitignore

@@ -1,6 +1,5 @@
 .yardoc
 pkg
-*.orig
 
 # ignore Gemfile.lock because we support multiple versions of Rails and
 # don't want to ship locked version requirements