add lines from official codeigniter download

- Added lines from the zip of Codeigniter-3.1.2

CodeIgniter.gitignore

+.DS_Store
+
 */config/development
 */logs/log-*.php
 !*/logs/index.html
 */cache/*
 !*/cache/index.html
 !*/cache/.htaccess
+
+user_guide_src/build/*
+user_guide_src/cilexer/build/*
+user_guide_src/cilexer/dist/*
+user_guide_src/cilexer/pycilexer.egg-info/*