update gitignore

- gemspec is useful information
- coverage isn't run anymore
- more aggressive blob for emacs and vim backup files

Author: Jerry Cheung

.gitignore

@@ -1,12 +1,7 @@
-spec/ldap.yml
+*~
+*.swp
 .rvmrc
-*.gemspec
 pkg/
-*.swp
-html/
 doc/
 publish/
-coverage/
-coverage.info
-.rake_tasks~
 Gemfile.lock